Electronic Surveillance in a Digital Age

July 1995

OTA-BP-ITC-149

GPO stock #052-003-01418-1
ii

Recommended Citation: U.S. Congress, Office of Technology Assessment, Electronic

Surveillance in a Digital Age, OTA-BP-ITC-149 (Washington, DC: U.S. Government

Printing Office, July 1995).
iii

oreword

awlessness and terrorism present new challenges to our society as the

21st Century approaches. Electronic surveillance is an invaluable tool

in America’s arsenal to fight crime in this era of high-speed, global

communications.

Digital communications technology has recently outpaced the ability of the

law enforcement agencies to implement court authorized wiretaps easily and

effectively. To address this problem, the 103d Congress enacted the Communications Assistance for Law Enforcement Act (P.L. 103-414). This Act invokes the assistance of the telecommunications industry to provide

technological solutions for accessing call information and call content for law

enforcement agencies when legally authorized to do so.

The law enforcement community and the telecommunications industry are

currently working collaboratively on solutions to implement the requirement

of the Act.

On September 27, 1994, Congressman Michael G. Oxley, a member or

OTA’s Technology Assessment Board, requested that OTA consider the technical aspects of implementing the law that will affect the ultimate cost to the government, the industry, and the rate payers.

This background paper reviews the progress of the industry and the law enforcement agencies in implementing the Act since its approval in October

1994. OTA extends its thanks to the Alliance for Telecommunications Industry

Solutions (ATIS) that sponsors the Electronic Communications Service Providers (ECSP) committee, which is the forum for the collaborative efforts of

the industry and law enforcement in seeking solutions for complying with the

requirements of the Act. Without the willful cooperation of the ECSP, OTA

would likely not have been able to accurately compile the information contained in this background paper.

Special acknowledgment is also given to the law enforcement community

for its assistance that was extended through the Telecommunications Industry

Liaison Unit (TILU) of the Federal Bureau of Investigation.

ROGER C. HERDMAN

Director
iv

roject Staff

Peter D. Blair

Assistant Director, OTA

Industry, Commerce, and

International Security Division

Andrew W. Wyckoff

Program Director

Industry, Telecommunications,

and Commerce Program

JAMES W. CURLIN

Project Director

ADMINISTRATIVE STAFF

Liz Emanuel

Office Administrator

Karry Fornshill

Secretary

Diane Jackson

Administrative Secretary

Karolyn St. Clair

PC Specialist

PUBLISHING STAFF

Mary Lou Higgs

Manager, Publishing Services

Chip Moore

Production Editor

Dorinda Edmondson

Electronic Publishing Specialist

Susan Hoffmeyer

Graphic Designer
v

1 Summary and Discussion 1

Congressional Request and Scope of the Study 6

The Communications Assistance for Law Enforcement

Act (P.L. 103-414) 7

Principal Features of the Act 8

Law Enforcement’s Requirements for Electronic

Surveillance 15

Findings and Observations 24

2 Technical Aspects of Electronic

Surveillance 29

Technologies 33

Switch-Base Solutions 35

Wireless Technologies 41

APPENDICES

A Section-by-Section Summary of the

 Communications Assistance for Law

 Enforcement Act Public Law 103-414 63

B Electronic Surveillance Requirements

 Keyed to P.L. 103-414 67

C Related OTA Reports for Further

 Reading 69

Glossary 71

ontents
Summary

 and

Discussion

he law enforcement community considers electronic surveillance1 to be an invaluable tool for fighting crime. Officials cite many instances where criminal activities were

either subverted, or if crimes were perpetrated, those responsible were apprehended as a result of court-approved electronic surveillance by law enforcement agencies.

The use of court-authorized electronic surveillance became increasingly more important as the telephone system became a part

of everyday life. For many years the law enforcement community

successfully matched its ability to perform electronic surveillance with the development of telephone technologies. The telephone industry worked cooperatively with law enforcement

agencies to ensure that access to specific communications was

available when the courts authorized such access.

When the telephone system was largely a network that connected handsets like the plain old black rotary dial telephones,

wiretapping was largely a simple procedure of physically connecting a listening or monitoring device to a circuit associated

with a telephone number. It was simple and inexpensive. But

times have changed. Technology has raced ahead, the structure of

the industry has changed, the number of carriers and services has

multiplied; dependence on communications for business and personal life has increased, computers and data are becoming more

1 For the purpose of this report electronic surveillance is considered to consist of both

the interception of communications content (wiretapping) and the acquisition of call identifying information (dialed number information) through the use of pen register devices

and through traps and traces.

| 1
2 | Electronic Surveillance in a Digital Age

important than voice traffic for business, and the

nation has become enthralled with mobile communication.

In 1984, AT&T was divested of its regional operating companies that made up the Bell System in

an antitrust settlement. Before then the American

telephone system operated on standards and procedures set by AT&T, with equipment that was

either built by its manufacturing affiliate or approved for use by the company. The system

worked uniformly and predictably throughout the

United States.

Prior to divestiture, the telephone system was

largely based on analog technology, with calls

originated and terminated over copper wires or

cables, which were directed to the receiver by

electrical contact switches. Microwave, and later

satellite, communications spanned distances that

copper did not cover through the 1960s. Those

days are gone. Analog technology is being replaced by digital technology, optical fiber is rapidly replacing copper cable, and computers are

replacing electrical switches for directing and

processing calls.

Computers are increasingly used to communicate with other computers that transmit and receive digital data and messages. Facsimile, still an

analog-based technology, has grown remarkably

as a preferred means of communication. Wireless

technologies, like cellular telephones, have

loosed the caller from the restraints of the telephone line, and has allowed freedom to communicate from autos, trains, boats, airplanes, and on

foot. In the future it is expected that personal communications systems will allow anyone, anywhere, to place phone calls via satellite linked to

the ground communication system. These developments have been precipitated by letting the innovative zeal of private entrepreneurs seek their

own visions of what the technology should be after the divestiture or AT&T and the deregulation

of the telephone industry. Many of the new developments have been made possible through the application of digital technology.

Transition from an AT&T-regulated monopoly

to the telecommunications system of the future—

i.e., a digitally based National Information Infrastructure (NII)—has been a process of chaotic

development. No longer do proprietary standards

and operating protocols of a monopoly provider

determine the architecture, functions, and procedures of the national telecommunications system.

Neither is it a certainty that one telecommunication device, standard, or transmission protocol

will work with another. Nor is there uniform delivery of compatible and interoperable services, e.g.,

Integrated Systems Digital Network (ISDN), to

all quarters of the country. Each of the Regional

Bell Operating Companies (RBOCs), the independent telephone companies, the interexchange

(long-distance) carriers, and the private competitive-access providers each have their own

business plans and schedules for deploying technologies. The United States has traded the

comfort of uniformity and predictability in its

communication system for creative innovation

and vigorous competition. The technological payoff for divestiture and deregulation has been large,

but progress has not been without a price to the

law enforcement community.

Access to electronic communications (both

wire other electronic communications) for law enforcement, i.e., court-approved wiretaps, pen registers, and traps and traces, are not simple or

routine procedures—neither technically, nor legally. (See box 1-A.)

Recent and continuing advances in electronic

communications technology and services challenge, and at times erode, the ability of law enforcement agencies to fully implement lawful

orders to intercept communications. These advances also challenge the ability of telecommunications carriers to meet their assistance

responsibilities. Thus, law enforcement agencies

are finding it increasingly difficult to deal with intercepted digital communication, which might

now be voice, data, images, or video, or a mixture

of all of them. Even the concept of the “telephone

number,” which at one time identified the target

subject of the court-ordered wiretap and was tied

to a physical location, may now only be a number

that begins the communication, then loses its

identity with an individual or location as the call

may be routed to others by the caller. Subscribers
Chapter 1 Summary and Discussion 13

Legal Authority

The Fourth Amendment of the U.S. Constitution protects Americans against unreasonable search and

seizure by the government. Each intrusion into the private lives of U.S. citizens by government entities

must fit within the Iimits prescribed by the U.S. Constitution as interpreted by the U.S. Supreme Court.

The evolution of the telephone system and wiretapping is one of the best examples of where technological development continues to challenge the Court and the Congress in balancing personal rights with public needs, In 1928, the Supreme Court first confronted the issue of whether wiretaps constituted “search” or

“seizure under the Constitution. (Olmstead v. United States, 48 S. Ct. 564, 277 U.S. 438) In the Instance of

Olmstead, the Court found that tapping a telephone did not violate the Fourth Amendment The case IS

best known, however, for the dissenting views of Justice Brandeis, who argued that wiretaps without a

court order or warrant violated a person’s right of privacy, which he defined as “the right to be let alone--

the most comprehensive or rights and the right most valued by civilized men. ” At the time of the O/instead

decision there were no wiretap statutes.

The Congress attempted to deal with the issue in the Communications Act of 1934. Siding with Justice

Brandeis’ views, the Congress included in Section 605 of the Act the provision that “no person not being

authorized by the sender shall intercept any communication and divulge or publish [its] existence, contents...or meaning. ” A series of cases followed passage of the 1934 Act, which interpreted various technical aspects of the law dealing, e.g., the admissibility of evidence, interstate and intrastate distinctions affecting the law, and individual rights of the called and calling parties.

By 1968 the provisions of the Communication Act of 1934 dealing with wiretapping were so muddled by

Interpretations of federal and state courts that the Congress decided to set forth a process and delimit the

legal authority of the law enforcement community’s authority to conduct wiretaps under Title Ill of the Omnibus Crime Control and Safe Streets Act of 1968. The procedures set forth in the 1968 Act define the authority and guide the conduct and procedures of wiretaps by federal law enforcement agencies. Thirty Seven

states have enacted parallel state statutes that define wiretapping authority within their jurisdictions. Many

of the states have laws more restrictive than those governing the federal authorities.

Telecommunications and computing technology continued to develop, so the Congress found it necessary to enact the Electronic Communications Privacy Act of 1986, which amended the Omnibus Crime

Control and Safe Streets Act of 1968 by broadening its coverage to include electronic communications (to

include electronic mail, data transmissions, faxes, and pagers). The provisions of Title Ill of the 1968 Act,

as amended, continue to govern the procedures for obtaining legal authority for initiating and conducting a

lawful interceptions of wire, oral, and electronic communications.

Procedure for Obtaining Court Order

It is more involved for law enforcement officials to obtain authorization to initiate and conduct a lawful

wiretap than it is to obtain a search warrant. A normal search warrant requires only that a law enforcement

official apply directly to a federal magistrate. Title Ill requires that a wiretap order be approved by the Attorney General, the Deputy, or an Assistant Attorney General of the Department of Justice before forwarding

to a local U.S. Attorney for application to a federal district court or other court of jurisdiction. Electronic

surveillance is only authorized for specific felonies that are specified in the Act, e.g., murder, espionage,

treason, kidnapping, bribery, narcotics, racketeering, etc.

Applications for electronic surveillance must show probable cause set forth in specific terms. It must

also be shown that the use of other normal investigative techniques can not provide the needed information, or that they would be too dangerous. The information in an electronic surveillance application must

(continued)
4 I Electronic Surveillance in a Digital Age

specifically state the offense being committed, the place or telecommunications facility from which the subject is to be Intercepted (special provisions are made for “roving” interceptions where the subject may be

highly mobile), a description of the types of conversations to be intercepted, and the identities of the person or persons committing the offenses and who are the subjects of the intercept. Thus, the Act focuses on

obtaining hard evidence to be used in prosecution, rather than general Intelligence

Court orders are normally valid for 30 days. Judges may also require periodic reports to the court advising it of the progress of the interception effort. A court may extend the order for an additional 30 days if

justified. Federal district court judges can authorize electronic interceptions within the jurisdiction of the

court where he or she presides. If the intercept subject is mobile or is using a mobile communications

device a judge may authorize electronic surveillance throughout the United States wherever the subject

may travel. A judge actually issues two orders. one authorizing the law enforcement agency to conduct the

interception; the second directing the service provider to set up the Intercept, specifying the telephone

numbers to be Intercepted and other assistance to be provided.

Under “emergency situations, ” e.g., serious and life-threatening criminality as defined in the Act, the

Attorney General and others specified in the Act, can authorize and emergency electronic surveillance that

if valid Immediately, but application for a court order must be issued within 48 hours. If a court does not

ratify the action and issue an order the intercept must be immediately terminated. Emergency intercepts

are rarely initiated.

Preserving Privacy and the Integrity of the Evidence

Intercepted communications are required to be recorded in a way that wiII protect the recording from

editing or alterations. Interceptions are required to be conducted in such a way as to “minimize the interception of communications not otherwise subject to interception. ” This Included unrelated, Irrelevant, and

non-criminal communications of the subjects and of others not named in the order.

Upon expiration of the intercept order, or as soon as practicable, the recordings are presented to the

court of jurisdiction and are sealed. Within a reasonable time period after interception, the subjects must

be furnished with an inventory of the recordings, and upon motion, a judge may direct that portions of the

recordings be made available to the subject for inspection.

Should the law enforcement agency err in conducting the electronic surveillance as authorized in the

court order, the intercept may be challenged, and if found to have been illegally conducted, the evidence in

the intercept may be suppressed.

SOURCE Title Ill of the Omnibus Crime Control and Safe Streets Act of 1968

at fixed locations can program the central office to switch, but are digital lines linked to routing tables

forward their incoming calls to other numbers

during certain times of the day or days of the week

or to forward or block calls originating from specific telephone numbers. Cellular telephones and

the next generation of mobile communication,

Personal Communication Services (PCS), enable

the caller to travel over great distances while

maintaining communications that are handed off

to other service providers. Modem communication systems are no longer wires connected to a

and computer databases that set up calls with other

computers almost instantaneously. It is an era of

intelligent networks, switch systems that do not

require physical connections, a digital environment that allows sophisticated encryption, and a

choice of communication modes from voice

through video. Persons might not communicate

verbally, but may instead use computers as intermediaries. Communication need no longer be

immediate, such as a conversation among individ-
Chapter 1 Summary and Discussion | 5

uals, but instead may be a computer message or a

voice message addressed to a “mailbox” that may

be stored, which can be accessed by another party

at a future time.

Law enforcement surveillance has become

more difficult and more expensive as a consequence of these new technological innovations.

What was once a simple matter of initiating a

court-approved wiretap by attaching wires to terminal posts now requires the expert assistance of

the communication service provider. Even the

once specific, but routine, requirements of the

courts to authorize a wiretap are today more complex because of modern communication technology.

There has been a sea change in communication

technology, and the law enforcement agencies

find it difficult to maintain electronic surveillance

as new services and features are added to the nation’s communication networks. During the late

1980s and early 1990s, the Federal Bureau of Investigation (FBI) and other law enforcement

agencies began to take steps to address the challenges posed by advanced telecommunications

technologies and services. By 1992, it was evident

that legislation would be necessary to ensure a level playing field and offer measures to address

compliance, security, and cost recovery. During

the 103d Congress, the Clinton Administration

proposed legislation to clarify the technical assistance provisions of existing electronic surveillance

statutes; and in October 1994, Congress passed

and the President approved the Communications

Assistance for Law Enforcement Act (P.L.

103-414).

The Act requires the telecommunication industry to assist the law enforcement agencies in

matching intercept needs with the demands placed

on them by modern communication technology.

The Act does not change the authority of the

courts to approve pen registers and traps and

traces2 as well as wiretaps, or for law enforcement

agencies to execute them under court order.3

Recognizing that existing equipment, facilities, or services may have to be retrofitted to meet

the assistance capability requirements, the law

provides that the Attorney General may agree to

pay telecommunications carriers for all reasonable costs directly associated with the modifications to those deployed systems. Accordingly, the

Act authorizes the appropriation of $500 million

over four fiscal years to reimburse telecommunications service providers for the direct costs of

retrofitting those systems installed or deployed as

of January 1, 1995. Generally speaking, costs for

achieving compliance for equipment installed after January 1, 1995, are to be borne by the telecommunications carrier for compliance determined to

be “reasonably achievable.” The Act also allows

for cost recovery for reasonable costs expended

for making modifications to equipment, facilities,

or services pursuant to the assistance requirements through adjustments by the Federal Communications Commission (FCC) to charges,

practices, classifications, and regulations in response to a carrier’s petition.

The combined cost to the telecommunication

industry and to the law enforcement agencies is

likely to be significant. However, supporters of

the bill during the congressional debate over the

Act in the 103d Congress cited the offsetting costs

to society caused by crimes that might result in the

absence of improving law enforcement’s capabili2 Pen register is an antiquated term. It stems from the manner in which the digits in a phone number were recorded when telephones used

pulse dialing technology, which has since been replaced by touch-tone technology. The term still applies to the recovery and recording of the

dialing information that addresses a call to and from an intercept subject. Authority for initiating a pen register or trap and trace surveillance is

found in 18 USC 3123.

3 Omnibus Crime Control and Safe Streets Act of 1968, Pub. Law No. 90-351, Title III. However, P.L. 90-351 only affects federal law enforcement agencies. Thirty-seven states have enacted some form of electronic surveillance laws to govern law enforcement agencies and courts

within the state’s jurisdiction. Many of the states’ electronic surveillance statutes are more stringent than the 1968 Federal Act. The remainder of

the states do not sanction wiretaps by their law enforcement entities.
6 | Electronic Surveillance in a Digital Age

ties to conduct electronic surveillance. Congress

considered the balance of costs and benefits and

determined that the benefits from crime prevention outweighed the costs of compliance.

Law enforcement believes that these costs will

not have a significant impact on either the shareholders or the customers of the telecommunications industry. They contend that costs not

compensated under the Act will be spread among

customers, and that the impact on the average telephone bill will be insignificant. While this may or

may not be true, the exact financial impact on the

government, companies, and their customers will

not be known until planning and implementation

process as set forth in the Act. At the time of this

report those costs are unknown.4

At a time when federal budgets are being

trimmed, the cost of electronic surveillance is

likely to increase sharply. Much of the cost of new

technology installed after January 1, 1995, will be

borne by the service providers and their subscribers. But there also will be a substantial financial

burden placed on state, federal, and local law enforcement agencies to conduct and maintain surveillance after the new technology is in place. The

Act does not address these costs.

CONGRESSIONAL REQUEST AND

SCOPE OF THE STUDY

On September 27, 1994, Congressman Michael

G. Oxley, a member of OTA’s Technology Assessment Board, requested that OTA consider the cost

factors of implementing the Communications Assistance for Law Enforcement Act (P.L. 103-414).

In his letter requesting the study, Mr. Oxley observed that during the debate preceding enactment, the costs of the legislation and who should

bear those costs were highly controversial issues.

Congress finally agreed to authorize $500 million over fiscal years 1995-98 for retrofitting the

service provider’s pre-1995 services, largely

based on its already installed switches (the Attorney General may cover costs for new equipment

based on technology that is not “reasonably

achievable” as determined by the FCC). The $500

million was a compromise among widely ranging

estimates from the telecommunication industry

and the law enforcement agencies. Both the industry and law enforcement’s estimates were based

on assumptions about costs for modifying existing equipment and deploying the technology, but

the estimates were generally not based on formal

engineering cost analysis. OTA further found that,

for practical purposes, it is not possible to develop

reliable cost figures without knowing what specific capacities for electronic surveillance the law enforcement agencies will place on the service

providers to meet their surveillance needs.5

The Act provides a process to obtain this information through the collaboration of the law enforcement agencies and the industry, but in the

meantime, the clock is running on the compliance

deadline, while the Attorney General’s capabilities and capacity notification to the industry that

will scope the requirements (and upon which costs

to the carriers will be determined) is not due until

October 1995. Priorities and capability statements

that must be prepared by the industry in response

4 On Aug. 11, 1994, Hazel E. Edwards, Director, Information Resources Management/General Government Issues, U.S. General Accounting Office, testified before the House Subcommittee on Technology and the Law, and the House Subcommittee on Civil and Constitutional

Rights, stating, “. . .it is virtually impossible to precisely estimate the reimbursement costs discussed in this bill because costs will depend on

evolving law enforcement requirements.” After careful study of the technological and operational factors involved in meeting the requirements

of the Act, and with information provided by the telecommunication industry and the law enforcement agencies in the course of compiling this

study, OTA reaffirmed the findings and conclusions of GAO in this regard.

5 The General Accounting Office (GAO) is assigned the responsibility under P.L. 103-414 (Sec. 112(b)(2)) provide cost estimates of the

expenditures expected by the telecommunication carriers to comply with the requirements of the Act. The Comptroller General is to report to the

Congress by Apr. 1, 1996, and every two years thereafter, progress for compliance with the Act and projections of future costs expected to be

incurred.
Chapter 1 Summary and Discussion | 7

to the Attorney General’s notification will follow

within 180 days. After this process is completed,

it will be possible to estimate the immediate costs

of complying with the Act.

This collaborative process involves two different types of organizations with differing goals.

Law enforcement agencies would like to be able to

execute authorized electronic surveillance without either technological impediments or delay.

Telecommunications carriers, on the other hand,

are reluctant to plan for modifications of their

equipment and facilities without an expectation

that they will be compensated for their costs. Consequently, in order to facilitate the collaborative

process, both parties consider the appropriations

authorized by the Act to be an important factor in

its success.

This study considers the technical factors that

will affect the rate of compliance with the requirements of the Act by the industry, and will provide

insights into the technical components that will

determine cost. OTA did not, and could not during

the period of this study, develop an aggregate cost

estimate for implementation of the Act. Only after

the Attorney General provides the notification of

law enforcement’s capacity needs to the service

providers and equipment manufacturers, and engineering cost analyses are done, will reliable and

meaningful cost estimates be available. It is

doubtful that such estimates will be available before the second quarter of 1996, given the time

schedule under the act. However, the description

of the technology and modifications required by

the act as summarized in this background paper indicate the scope and complexity, and hence the

likely subjective magnitude of the costs involved.

During the debate preceding enactment, considerable attention was given to sensitive issues of

privacy and personal rights and protections. This

report does not address these issues. OTA’s commission to undertake this study considers only

those technical factors that enter into the cost and

deployment of the technologies required of the

telecommunications industry by the Act and the

operation of the National Information Infrastructure (NII) of the future as it may affect the surveillance missions of law enforcement agencies.

THE COMMUNICATIONS ASSISTANCE

FOR LAW ENFORCEMENT ACT

(P.L. 103-414)

An affirmative obligation for telecommunication

service providers to assist the law enforcement

community in authorized electronic intercepts has

existed since Congress amended Title III of the

1968 Omnibus Crime and Safe Streets Act in

1970.6 This amendment clarified an ambiguity in

the 1968 law about the specific responsibility of

telecommunications carriers for assisting law enforcement agencies in authorized wiretaps.7 The

Supreme Court in United States v. New York Telephone, 434 U.S. 159, 177 (1977) found that 18

U.S.C. 2518(4) required the federal courts to compel telecommunication providers to provide “any

assistance necessary to accomplish an electronic

interception.” The question of whether a carrier

has any obligation to design its equipment to facilitate an authorized electronic surveillance under

18 U.S.C 2518(4) was never litigated.

It was not until the technology explosion in the

communication industry in the 1980s made it

more difficult for law enforcement agencies to

conduct authorized wiretaps that the issue of design requirements arose. The Communications

Assistance For Law Enforcement Act makes it

clear that the service providers must now consider

equipment and system design as well as the capability to provide the call content and call identification information needed by law enforcement

6 See 18 U.S.C. 2518(4). The amendment requires the service provider “furnish. . .information, facilities, and technical assistance necessary

to accomplish the interception. . . . .” The amendment further provides that a cooperating service provider “. . .be compensated. . .for reasonable expenses incurred in providing such facilities or assistance.”

7 In 1970 the Ninth Circuit Court of Appeals found the 1968 Act did not provide the necessary statutory authority of law enforcement agencies to compel the telephone companies to assist in wiretaps. (Application of the United States, 427 F. 2d 639 (9th Cir. 1970).
8 | Electronic Surveillance in a Digital Age

agencies, and the capacity that the law enforcement agencies need to simultaneously intercept a

specified number of wiretaps. The Act also establishes a process for reimbursing the service providers for their expenses in meeting law

enforcement’s needs. (See appendix A, Sectionby-Section Summary)

PRINCIPAL FEATURES OF THE ACT

❚ Coverage and Exclusions

All “telecommunications carriers” that are considered common carriers must comply with the requirements of the Act.8 This includes local

exchange carriers, competitive access providers

(CAPs), interexchange carriers, cellular carriers,

providers of personal communication services

(PCS), and other mobile radio services. Cable

companies and electric utilities companies would

be covered if they provide telecommunications

services for hire to the public.

Companies providing “information services”

are excluded from the Act’s requirements. Such

services include electronic messaging services,

e.g., electronic mail, electronic forms transfer,

electronic document interchange (EDI), information and databanks available for downloading by a

subscriber, and Internet service providers.

❚ Capabilities Required

A telecommunications carrier must have the capability to selectively isolate and intercept real-time

electronic traffic and call identification information and deliver it in the appropriate format to law

enforcement personnel off the carrier’s premises.

The service provider may not reveal the physical

location of an intercept subject, other than that information available from a telephone directory

number, unless so authorized by court order. A

carrier must be able to notify a law enforcement

agency, during or immediately after the transfer of

control of the communication to another carrier.

Carriers are not responsible for decryption unless

they have provided that encryption service to the

intercept target. (See figures 1-1A, 1-1B.)

❚ Capacity Requirements

By October 25, 1995, the Attorney General must

notify the carriers of the law enforcement agencies’ specific capacity needs, i.e., the number of

simultaneous interceptions that must be planned

for within each service provider’s system. This is

expected to vary among the service providers,

with higher capacities required in larger urban

areas, such as the New York Metropolitan area,

Miami, Los Angeles, etc., while few or no requirements may be placed on those carriers serving

some rural areas. On the other hand, cellular and

other mobile communication carriers may be required to equip a large proportion of their switches

with wiretap capabilities so that taps on intercept

parties may be linked as they roam among service

areas.

The Attorney General must provide the carriers

with two estimates of needed capacity:

a. an actual capacity that covers the period

through October 25, 1998, and

b. an estimate of maximum capacity that would be

required on October 25, 1998 and beyond.

The Attorney General is to periodically review

law enforcement’s needs and notify the industry of

any changes in maximum capacity.

Within 180 days after the Attorney General

publishes the capacity notifications, service providers must provide statements that identify those

areas where the carrier does not have the capacity

to simultaneously accommodate the types of surveillance required. (See figure 1-2.)

❚ Time for Performance

Within three years after the Attorney General notifies the carrier of the initial capacity needed by the

law enforcement agencies, a carrier must be able

to provide the number of simultaneous intercep8 A Common Carrier is a company that furnishes public telecommunications facilities and services, e.g., a telephone or telegraph company.

A Common Carrier cannot control message content.
Chapter 1 Summary and Discussion 19

Create technical

requirements through

Technical

industry association requirements

or standards setting

adopted

organization A

Attorney General

consultative

process FCC petitioned

to establish r

Attorney General

determines law

enforcement capability

and capacity

requirements

Carrier proposes

modification

technical

requirements

no

Carrier files for

an extension

from FCC if

compliance not

reasonably achievable

Carrier submits

claim in Government Carrier adds

accordance with pays capacity

payment regulation

SOURCE Federal Bureau of Investigation, 1995
10 I Electronic Surveillance in a Digital Age

Attorney General

establishes

payment

regulations

SOURCE Federal Bureau of Investigation, 1995

tions specified (this date will likely be in late FCC agrees that compliance is not reasonably

1998). After that time, service providers must be achievable within that time span, the FCC may

capable of increasing the number of simultaneous grant an extension of up to two years (circa 2000).

interceptions up to the maximum number deter- (See figure 1-3.)

mined by the Attorney General. A carrier may

petition the Federal Communication Commission ■ Collaboration

(FCC) for an extension of the compliance dead- Carriers, manufacturers, and vendors are encourline if meeting the capability requirements is not aged to collaborate among themselves and with

reasonably achievable by the 1998 deadline. If the
Chapter 1 Summary and Discussion 111

Attorney General Attorney General

provides publishes capacity

notice/ > requirements in

comments Federal Register

Carrier submits

claim in

accordance with

payment

Government

pays

Carrier in Carrier adds

compliance capacity

I I

I (

SOURCE Federal Bureau of Investigation, 1995

the law enforcement agencies in developing and

modifying technology and equipment to meet law

enforcement needs. The Attorney General represents the federal and state law enforcement agencies in the collaborative process. As the

representative of law enforcement, the Attorney

General must consult with industry associations,

standards-setting organizations, telecommunication users, and state regulatory commissions to facilitate implementation of the Act. The Federal

Bureau of Investigation (FBI) has been given the

authority for implementing the Act.

Carriers and manufacturers are protected from

the risk of being judged in noncompliance of the

capability requirements if they adopt an accepted

technical standard, or an agreed upon industrygovernment technical solution. However, the absence of such standards or technical solutions

does not relieve the industry of its obligations under the Act.
12 I Electronic Surveillance in a Digital Age

Attorney

General’s

report to

Date of Congress and

enactment to public

1 0/25/94 1 1/30/95

Capability

statements Effective

due from date for

the carriers compliance

4/23/96 10/24/98

1/1 /95 Capacity

notices

due from

the Attorney

Attorney Effective

General’s date for

report to compliance

Comptroller following an

General General

■ Actual 4/1/96

■ Maximum

10/24/95

extension

10/24/2000

SOURCE Federal Bureau of lnvestigation, 1995

If voluntary standards or technical solutions are

not available, or if an adopted standard or solution

is judged by anyone to be deficient, the FCC may

be petitioned (by any person or entity) to establish

the necessary technical requirements or standards

to allow compliance with the Act.

■ Cost Reimbursement

The Attorney General is authorized to pay the

direct costs for modification of equipment, facilities, or services necessary to meet the requirements of the Act for equipment deployed prior to

January 1, 1995, and for costs of modifications after that date if they are determined to be not “reasonably achievable.” Five hundred million dollars

($500 million) is authorized to be appropriated

over four fiscal years, 1995 through 1998.9

If the Attorney General does not agree to reimburse a carrier that requests compensation, the carrier is considered to be in compliance with the Act

until that equipment is replaced or significantly

upgraded, or otherwise undergoes major modification.

For equipment deployed after January 1, 1995,

a carrier must assume the expense of complying

with the Act unless to do so is not reasonably

achievable, i.e., that compliance would impose

“significant difficult y or expense” on the carrier or

users.

10 The FCC would determine whether compliance would be reasonably achievable or not.

If compliance is deemed by the FCC not to be

reasonably achievable, the Attorney General may

agree to pay the carrier for costs of developing the

capability to comply with the Act. If the Attorney

General does not agree to pay such costs, the carrier is considered to be in compliance with the

Act.11

9 The Congressional Budget Office (CBO) projected that outlays for the $500 million authorized by the Act would be $25 million for FY

1995,$100 million for FY 1996, and $375 million for FY 1997. Senate Committee on the Judiciary, Report on S.2375, The Digital Telephony

Bill of 1994, Report 103-402, p. 33, 103d. Cong., 2d sess., Oct. 6, 1994.

10 If the Attorney General decides to pay the costs for modifications made after Jan. 1, 1995, that are determined to be not reasonably achievable, the government is obligated to pay the carrier only “for the additional cost of making compliance with the assistance capability requirements reasonably achievable.” [emphasis added]

11 Id., CBO estimates that additional authorizations of $100 million will be required for each of the fiscal years 1998, 1999.
Chapter 1 Summary and Discussion | 13

The Act (through an amendment to the Communications Act of 1934) allows for cost recovery

for continued compliance with the Act to be built

into the rate structure for interstate and foreign

communications under the jurisdiction of the

FCC. (Sec. 229(e)) Tolls and rates for intrastate

communications are largely determined by the

states, and the Act does not directly address cost

recovery through intrastate rate adjustment.12

❚ Implementation of the Act

Since January 1992, when President Bush authorized the Department of Justice to proceed with

legislation that led to the enactment of P.L.

103-414, law enforcement officials have been

working with the telecommunication industry to

solve the problems associated with electronic surveillance in a digital, high-speed communication

environment.13 In July 1992, the FBI, as spokesman for all federal, state, and local law enforcement agencies, published a document entitled

Law Enforcement Requirements for the Surveillance of Electronic Communication. The document outlined law enforcement’s requirements for

the surveillance of electronic communications

and still continues to guide the framework for

government/industry collaboration, though updated several times since then.14 (See appendix

B.)

In general, the telecommunication industry has

been compliant with regard to law enforcement’s

concerns for maintaining wiretap capabilities in

the face of technological development. The major

initial sticking point in complying with the need

of the law enforcement community concerned

who would be financially liable for meeting law

enforcement’s needs. The companies would not

unilaterally invest money or technical resources to

seek solutions to the problems in the absence of a

legal mandate that would ensure that competing

companies would be held to the same requirements. Many, but not all, of the industries’ concern about reimbursement and fairness were dealt

with in the legislation. Recently, however, the industry has been more concerned with how law enforcement’s capacity requirements will impact

costs, and hence their future financial liability.

The 1994 Act authorizes the appropriation of

money for cost reimbursement to meet law enforcement’s requirements, and contains a fail-safe

provision that relieves a carrier of its obligations

under the Act if money is not provided to offset the

cost of compliance. Furthermore, a “safe harbor”

provision holds a carrier blameless if it deploys a

technical solution to meet law enforcement’s requirements that has been approved by a government-industry group, an industry trade group, or a

standard setting authority capable of meeting law

enforcement’s capability requirements under Section 103 of the Act.

The Attorney General has delegated much of

the responsibility for implementing the Act to the

FBI. To facilitate implementation, the Director of

the FBI has created the Telecommunication Industry Liaison Unit (TILU) made up of 70 to 80

persons and specialists to coordinate the efforts of

the federal, state, and local law enforcement agencies in collaborating with the industry. TILU is intended to be a one-stop point of contact for all

matters dealing with compliance with the Act.

12 Section 301 of the Act added Section 229 to the Communications Act of 1934 by directing the FCC to convene a federal-state joint board

to recommend appropriate changes to the FCC’s separations rules. Regulated carriers will seek to recover costs through rate adjustments at the

state level, and unregulated carriers will likely pass the costs to the customers.

13 Testimony of Louis J. Freeh, Director, Federal Bureau of Investigation, before the U.S. Senate, Committee on the Judiciary, Subcommittee on Technology and the Law, and the U.S. House of Representatives, Committee on the Judiciary, Subcommittee on Civil and Constitutional

Rights, Mar. 18, 1994, 103d Cong., 2d sess.

14 The FBI’s “Requirements” Document is in its fourth revision. The second revision was June 1994 (at that time it outlined nine requirements), the third revision (rev. 2.1), made Dec. 6, 1994, keyed the Law Enforcement’s requirements to the organization of the 1994 Act, and

combined the nine requirements into four in order to parallel the organization of the Act. The most recent revision was issued in May 1995.
14 | Electronic Surveillance in a Digital Age

Technical matters, cost reimbursement, compliance with capabilities and capacity, liaison with

service providers and switch manufacturers/vendors, etc., are to be coordinated through this unit.

Even before the Act was passed, the law enforcement agencies and the industry had begun a

collaborative effort to confront the problems of

electronic surveillance. Building on earlier consultation with the industry through an informal industry technical working group that was convened

more than two years before passage of the Act, a

more formal arrangement was struck, which currently serves as the primary focus of government/

industry collaboration.

In March 1993, the Electronic Communications Service Provider (ECSP) Committee was

formed under the aegis of the Alliance for Telecommunications Industry Solutions (ATIS), an

industry group aimed at resolving issues involving telecommunications standards and the development of operational guidelines.15 The ECSP

committee is co-chaired by an industry official

and a representative of the Attorney General who

represents the collective views of federal, state,

and local law enforcement agencies.

ECSP is an open forum with over 200 individual participants (however, only 40 to 60 persons

have consistently participated in the action

teams), consisting of representatives of local exchange carriers, interexchange carriers, trade

associations, industry consultants, equipment

manufacturers, and law enforcement officials,

among others.16 Each participant must sign a nondisclosure agreement that is intended to both

guard information that might be useful to the

criminal element and to reduce the risk of divulging proprietary information, while ensuring a free

and open forum for discussing mutual problems.

ECSP has created six action teams, each cochaired by a representative of the industry and a

representative of the law enforcement agencies:

 Advanced Intelligent Networks (AIN): Addresses solutions to problems related to the

next-generation telephone network now in the

initial stages of deployment. AIN involves the

deployment of software-controlled devices, including signaling systems, switches, computer

processors, and databases. These functional

units enable subscribers to independently configure services to meet their needs, and in doing

so, create another layer of complexity for wiretapping.

 Personal Communication Services (PCS):

Considers solutions to problems arising from

development of the next generation of wireless

communication with the possible future capability of spanning the world.

 Prioritization and Technology Review: Responsible for establishing the priorities in attacking the problems associated with the

various communication technologies. The action team is also charged with identifying future emerging communication technologies

and features that must be dealt with in the future.

 Switch-Based Solutions: Develops recommendations to meet the functional requirements for

the central switch office-based solutions to

meet law enforcement’s requirements, including operational security.

15 Alliance for Telecommunications Industry Solutions (ATIS), 1200 G Street, N.W., Suite 500, Washington, DC 20005. Other industry

associations have also been instrumental in developing the working relationship between the law enforcement agencies and the industry, including United States Telephone Association (USTA), Telecommunications Industry Association (TIA), and the Cellular Telecommunications

Industry Association (CTIA), and other industry standards-setting bodies.

16 ECSP does not include all of the industry groups involved in compliance with the Act. Many accredited standards-setting organizations

and other trade organizations will play a role meeting technical and operational compliance requirements. One example of this is the Telecommunications Security Association (TSA); an association of security officials from the service providers that are responsible for executing authorized wiretaps for their respective companies. Individuals from this organization are involved in the ECSP effort, however.
Chapter 1 Summary and Discussion | 15

 Interfaces: Assesses the requirements for

physical, messaging, operational, and procedural interfaces to meet the needs of the law enforcement agencies.

 Cellular: Considers cellular technologies in the

context of law enforcement’s intercept requirements.

The objective of the action teams is to explore

the implications of meeting law enforcement’s

electronic surveillance requirements on the telecommunications networks. To assist them in their

objectives, they are preparing a series of consensus documents to serve as references for industry

standards-setting bodies, service providers,

equipment manufacturers, and law enforcement

agencies. These documents, which are to be produced by each action team, will generally include:

 Requirements and Capabilities Document,

 Interpretation of Requirements Document,

 Features and Description Document, and

 User Performance Document.

Industry standards groups will use these documents to develop standards specifications that

will guide manufacturers in the development and

production of switches and other devices needed

to meet the requirements of the law enforcement

agencies.

LAW ENFORCEMENT’S REQUIREMENTS

FOR ELECTRONIC SURVEILLANCE17

The requirements of the law enforcement agencies

apply to all forms of electronic communications

service providers. The requirements are, however,

generally couched in terms that apply primarily to

telephone communication. Nonetheless, the same

requirements apply to any industry sector that provides common carriage of communications for

sale, including the cable television industry, public utilities, and other forms of electronic communication, except information service providers,

which are expressly exempted under the act.

These requirements, though stated in legal or

descriptive terms based on Section 103 of the Act,

when translated by engineers and service personnel into technical requirements, impose stringent

and substantial challenges to equipment manufacturers and the service providers for meeting law

enforcement’s needs.

❚ Communications Access

Each service provider is required to have procedures capable of activating and deactivating wiretaps within 24 hours after receiving a lawful

intercept request. Law enforcement agencies may

also require expeditious access to technical resources or assistance in activating the intercept or

to obtain needed service information. In “emergency situations,” (e.g., in cases where rapid response is required to eliminate threats to life,

property, or national security) law enforcement

agencies require access to the intercept subject’s

communication, and technical assistance within a

few hours.

Law enforcement agencies require access to all

electronic communications transmitted and received by an intercept subject. Access must be

provided from anywhere within the service area of

a service provider. Access to all call setup information necessary to identify the calling and

called numbers, e.g., originating line number

identification, and terminating line number identification for all completed and attempted calls, as

well as access to the call content is required. Under

this requirement, the carrier remains in custody of

the call service, with the carrier’s security personnel activating or deactivating an intercept only

when presented with legal authority by a law

enforcement agency. Law enforcement agencies

require that the service providers have a 24-hour17 This section of the report relies heavily on the material contained in the document “Law Enforcement’s Requirements for Electronic

Surveillance,” May 1995 revision, pp. 2-14, Federal Bureau of Investigation, Washington, D.C. It should be noted that these requirements represent the law enforcement agencies’ interpretation of the requirements under the Act. Some service provider’s disagree with some of the interpretations presented in the FBI requirements document cited above.
16 | Electronic Surveillance in a Digital Age

per-day capability of accessing and monitoring simultaneous calls originated or received by an

intercept subject at the moment the call is taking

place.

Law enforcement agencies require carriers to

provide for implementing multiple simultaneous

intercepts within a service provider’s system, central office or area.18 This requirement includes the

ability for different law enforcement agencies to

simultaneously monitor the same intercept subject while maintaining confidentiality among the

agencies. Each carrier is required to support all requested authorized intercepts within its service

area. To meet these requirements, service providers are required to have reserve intercept capacity

available to meet unexpected demands, which are

to be set forth by the Attorney General on or before

October 25, 1995. Law enforcement agencies

need to be able to access and monitor simultaneous calls placed or received by an intercept subject without the intercept being detected.

The service provider is only responsible for access as long as the call is under its control or maintains access to the call. If the original service

provider does not maintain access to the ongoing

call, it is that service provider’s responsibility to

provide any available information to law enforcement that identifies the visited service area and/or

carrier. Once handed off to a second service provider, it is the second provider’s responsibility to

provide the access to law enforcement. The originating carrier, however, must notify the law enforcement agency to which carrier the call has

been handed off.

Access is specifically required for call identifying information.

Call identifying information includes, for example:

 information concerning an intercept targets

connection or transmission path to the network,19

 information concerning a calling party’s connection or transmission path to the network

when in contact with the intercept subject,

 dialing and signaling information generated by

the intercept subject,

 directory numbers used in transferring or forwarding calls, and

 notification that a call or call attempt has occurred.

The nature and type of call setup information

will vary depending on what type of communication service the calling or terminating party is using, i.e., information available from a call

originated from a cellular phone will be different

than if the call originated through a wired system.

(See table 1-1.)

❚ Dialing and Signaling Information

Law enforcement requires access to all dialing and

signaling information for all calls originated by

the intercept target, e.g., all digits dialed by the intercept subject and any information used to establish or direct call flow. In addition, after the call is

completed (cut-through), law enforcement requires dialing information generated by the subject, e.g., touch-tone digits dialed to activate or

code a device at the point of call termination.

Examples of dialing and signaling information

include:

 All digits dialed by the subject and any signaling information used to establish or direct call

flow, e.g., activating service features like call

forwarding or three-way calling.

 Subsequent dialing information generated by

the subject after cut-through (connection), e.g.,

dialed digits, voice dialing, etc.

 The terminating or destination number derived

by the originating switch based on its interpretation of the subject’s dialed digits or other

call direction commands.

18 The number of simultaneous intercepts that a particular switch or system can accommodate is referred to as “capacity.”

19 “Transmission path” refers to connection or link from a subscriber’s terminal to the network. The path may be over a wireline or radio link.
Chapter 1 Summary and Discussion 117

Calling Party’s Intercept Subject’s

Line Information Service Type Line Information

■

■

■

■

■

■

■

■

■

■

■

■

Directory Number

Associated Directory Number

Line Equipment Identifier

Call Type/Bearer Capability

Service Profile Identifier (SPID)

Numbers used by the service provider

switch to identify the PBX and the caller

behind the PBX

—Directory Number of the PBX

—Station identifier of the calling party

(if available)

Directory Number

Electronic Serial Number (ESN)

Mobile Identification Number (M IN)

Personal Number/Directory Number

Terminal Equipment Identifier

Directory Number

Plain Old Telephone

Service (POTS)

Integrated Services

Digital Network (ISDN)

Private Branch

Exchange (PBX)

Coin

Cellular

Personal Communications Services (PCS)

Other Special and Proprietary Customer Premises Equipment (CPE)

Interfaces (Non-POTS

or Non-lSDN Signaling)

Directory Number (DN)

Associated Directory Number

Line Equipment Identifier

Call Type/Bearer Capability

Service Profile Identifier

Numbers use by the service provider

switch to identify the PBX and the caller

behind the PBX

—Directory Number of the PBX

—Station identifier of the called party

(if available)

Directory Number

Electronic Serial Number (ESN)

Mobile Identification Number (M IN)

Personal Number/Directory Number

Terminal Equipment Identifier

Directory Number

Other available items, for example, Automatic Numbering Identification (ANI)

SOURCE Federal Bureau of Investigation.

Redirection Numbers

Access to call setup information includes redirection numbers when calls are forwarded or transferred using custom calling features, for example

when multiple forwards or transfers are involved

in a call attempt. A call initiated by a calling party

to the intercept subject maybe forwarded or transferred several times before reaching the intercept

target. In those cases, law enforcement requires

the number of the party that originated the call,

and any intermediate numbers used to redirect the

call. 20 Access is required to forwarded-to numbers if control of the call remains with the service

provider executing a lawful wiretap.

Call Attempt Alerts

Notification of all call attempts placed by or to the

intercept target are required. Currently, in the case

of wireline communications intercepted in a local

exchange carrier’s (LEC) service area, law enforcement agencies generate a time stamp after automatically detecting signals for ringing, or when

a receiver is taken off or placed back on its hook.

New technologies will make the simple detection

20 According to industry representatives participating in the ECSP, current network signaling can provide the Original calling number, the

original called number, and the last redirected number. It is not considered to be technologically feasible with existing standards for interswitch

signaling to provide more than this unless the entire signaling system is changing to provide these capabilities.
18 | Electronic Surveillance in a Digital Age

methods more difficult as out-of-band (i.e., offline) signaling using computer-controlled signal

transfer points replaces conventional in-band (online) signaling systems commonly used by many

local exchange carriers today. Therefore, law enforcement agencies will require some form of notification from the carrier so that monitoring

equipment can be activated.

Call Content

Law enforcement agencies must have access to

the contents21 of calls placed or received by intercept subjects. In some modes of transmission, the

electronic communication may be carried on two

different channels (duplex), with one party on one

channel, and the other on a second channel. Nonetheless, the carriers must provide uninterrupted

access to both channels simultaneously.

There are three possible combinations for placing and receiving calls:

 wireline-to-wireline, including Plain Old

Telephone Service (POTS), coin operated service, and Integrated Service Digital Network

(ISDN);

 wireline-to-mobile or mobile-to-wireline, where

one party uses a cellular, PCS service or other

wireless service, and the second party uses a

wireline service; and

 mobile-to-mobile services, where both parties

use cellular, PCS service or other wireless service (See figure 1-4.)

Custom calling features allow subscribers to

forward or redirect their calls, or set up conference

calls involving more than two parties. In these

cases, a service provider is required to provide access to the call so long as it maintains access to the

communications. If a call from an intercept target

is redirected so that the authorized service provider loses access to the call, the provider must notify

the law enforcement agency of the identity of the

service provider who then has custody of the intercept call. If the new service provider’s identity is

not known, the carrier must provide any supplemental information that would assist the law enforcement agency in determining the new service

provider’s identity.

Mobile Communications

Requirements for accessing call setup information and call content apply to both wireline and

wireless mobile communications. A mobile customer can move freely about a home service area

and beyond into the service area of another mobile

carrier. A service provider’s network may cover a

local area, a region, a state, or portions of a multistate area. When a single service provider covers a

large geographic area, that carrier is required to

provide access to an intercept subject’s communication wherever it takes place within the provider’s extended service area consistent with the

court order authorizing the intercept. Law enforcement agencies require access to an intercept

subject’s communications throughout the area

served by his or her home service provider. When

an intercept subject travels into another service

provider’s area while communicating, law enforcement agencies require access to the ongoing

call so long as the home service provider maintains access to the call in progress. If access to the

call is not maintained by the home service provider, law enforcement agencies require that the identity of the service provider to which the call was

handed off be made available, or that information

be provided that will enable the new service provider to be identified. (See figure 1-5.)

The discussion above focused on the case

where a mobile intercept subject originated a call

in his or her home service provider area and traveled to an adjacent service provider’s area in the

course of a call, and the call is handed off to another service provider.

Subscribers who “roam” beyond their home

service provider’s area and attempt to establish

communication from another service provider’s

21 “Call content” refers to any type of electronic communications sent by or sent to the intercept subject, including transfer of signs, signals,

writing, images, sounds, data, or intelligence of any nature.
Chapter 1 Summary and Discussion 119

Wireline-to-Wireline Call

Wireline Local exchange Local exchange Wireline

phone end office end office phone

Wireline-to-Mobile or Mobile-to-Wireline Call

Wireline Local exchange Mobile Cell site Mobile unit

phone end office telephone

switching

office

Mobile-to-Mobile Call

Mobile unit Cell site Mobile Cell site Mobile unit

telephone

switching

office

SOURCE Federal Bureau of Investigation, 1994

area are registered as visitors in the new service. In

those instances, information about the caller’s

unique Electronic Serial Number (ESN) and Mobile Identification Number (MIN) and other authentication, validation, and routing information

are automatically exchanged between the location

registers (computer databanks) of the two cellular

service providers. (See figure 1-6.)

Law enforcement agencies require access to information regarding the identity of service providers that request visitor’s registration authorization

from an intercept subject’s home service provider.

The home service provider must provide the law

enforcement agencies with the visited service provider’s identity, and other data, such as service site

information of the carrier that is controlling the intercept subject’s communication.

■ Delivery of Information

to Law Enforcement

Law enforcement agencies require that call content and call setup information that is intercepted

in response to an authorized wiretap be trans-
20 I Electronic Surveillance in a Digital Age

SOURCE Federal Bureau of Investigation, 1994.

mitted to a designated law enforcement monitoring facility. However, access to the intercept will

be controlled by the service provider and not the ■

law enforcement agency. Transmission of intercepted communications must satisfy the following guidelines: ■

■ Where call setup information and call content

are separated during interception, the service

provider must take steps to ensure accurate

association of call setup information with call

content.

Transmission of the intercepted communication to the monitoring site must be made without altering the call content or meaning.

Law enforcement agencies require that the

transmission facilities and formats of the information transmitted the monitoring stations

be in a standard form.
Chapter 1 Summary and Discussion 121

●

■

Home Cellular Network

Home location

ESN, MIN, Routing alias,

Authentication/Validation

Visited location

Registration

notification, Visited Cellular

Routing request, Network

Profile request

Mobile telephone

switching office

SOURCE Federal Bureau of Investigation, 1994

If the service provider controls and/or provides

coding, compression, encryption, or other

security features for the intercepted communications, the service provider must decode,

decompress, or decrypt intercepted messages

before transmission or provide the capabilities

to the law enforcement agency to reprocess the

information.

Law enforcement agencies require that the service provider use a minimum number of transmission facilities to deliver the intercepted

communications to the monitoring facility.

Currently, most cellular service areas with multiple Mobile Switching Centers (MSC) require

a connection from each MSC to the monitoring

location for each intercepted call.

■ Verification Information

Law enforcement agencies require that the carrier

provide information to verify or authenticate the

linkage between the intercepted communications

and the intercept subject in order to establish the

wiretap as evidence in court, however, it is law enforcement’s responsibility to authenticate the

linkage. Prior to implementation of the intercept,

the service provider is obligated to provide the law

enforcement agency with information on the services and features subscribed to by the intercept

subject (service profile).

Courts require law enforcement agencies to

verify that the communication that was monitored

was that of the intercept subject authorized in the
22 | Electronic Surveillance in a Digital Age

lawful authorization of the wiretap. This is done

with a network identifier (directory number), terminal identifier, personal identification number,

and billing and caller identification-related information.

Service profile information, i.e., the service

subscribed to by an intercept subject, must be

made available to a law enforcement agency in response to a lawful inquiry before and during an intercept. Service providers are obligated to notify

the law enforcement agency of changes in the intercept subject’s service profile during the progress of an interception, even if the change is

initiated directly by the intercept subject without

the involvement of the service provider, e.g., call

forwarding.

Reliability of Service

Reliability of service for intercepted communications delivered to a law enforcement agency must

be of equal reliability as that of the intercept subject’s service. Service providers must also have

the ability to detect and solve problems with the

interception of call setup information or content

information, as well as the transmission of the intercepted information to the law enforcement

monitoring facility.

Quality of Service

The quality of the service supporting the intercept

must be at least equal to the quality of the service

provided to the intercept subject, measured by any

objective factor, e.g., signal-to-noise ratio, bit error rate, or other parameters that measure transmission quality.

Transparency of Interceptions

Intercepts must be undetectable by the intercept

subject or other callers, and known only to the

monitoring law enforcement agency and authorized personnel of the service provider responsible

for setting up the intercept. In some cases, intercept subjects may use sophisticated equipment to

detect intercepts; nonetheless, service providers

are obligated only to provide transparency within

the limits of their equipment based on industry

standards for transmission characteristics. Benchmarks for meeting the transparency requirement

include:

 The subject should not be able to discern that an

intercept is in progress.

 If the intercept begins during a call in progress,

the intercept should not disrupt or interrupt the

ongoing call.

 If in the process of interception, changes in services or features occur, these changes should

not be apparent to the intercept subject or other

parties

 Any line noise introduced by the intercept

should not be perceptible to the intercept subject or other parties.

❚ Network and Intercept Security

Service providers are also required to adopt operating procedures that safeguard against unauthorized or improper intercept and to prevent

compromise of transparency. Such procedures include:

 internal restrictions on information about intercepts,

 security mechanisms for activating and deactivating intercepts,

 physical security to limit access to systems supporting intercepts,

 procedures to prevent disclosure of service

changes caused by implementation of intercepts, and

 restrictions on knowledge of the existence of

intercepts among service provider’s employees.

Network security and integrity is addressed in

Section 105 of the Act.22 The Act directs that only

an employee of a service provider can activate an

intercept after the receipt of a lawful authorization

from a law enforcement agency, according to procedures prescribed by the Federal Communica22 Section 301 of the Act also directs the FCC to establish rules to implement Sec. 105.
Chapter 1 Summary and Discussion | 23

tion Commission (FCC). (Sec. 229(b)) However,

other security matters not addressed by the Act

figure prominently in maintaining network security protecting the integrity of electronic surveillance.

Computer systems, in general, are susceptible

to breaches of security under the most strict controls. This is evident from the violation of even

relatively secure computer systems and networks

within the Department of Defense. The modern

telephone network is little more than an extension

of a series of interconnected wide-area computer

networks linked by transmission facilities. As

such, telephone systems suffer the same vulnerabilities as all networked computer systems.23

Whether or not the network may become more

vulnerable as a consequence of meeting law enforcement’s intercept requirements under the Act

is uncertain. There is no empirical evidence that

suggests that it will at this time.

The complexity of sophisticated computer systems is their source of vulnerability. Millions of

lines of computer code are needed to operate a

large networked computer system. The magnitude

of the operating system creates hundreds of potential opportunities or windows for penetrating the

system. On the other hand, a proficient person intent on hacking into the system need only find one

of these windows to achieve his or her objective.

Maintaining a secure operational environment

in the administration of electronic intercepts is a

major concern in wiretap procedures. Security

problems exist whether the intercept involves

switched landlines, mobile cellular operations, or

personal communication services. Security protocols are needed to prevent unauthorized personnel

from: Initiating or terminating surveillance; obtaining information about a surveillance in progress; monitoring the results of a surveillance;

determining past surveillance activities or acquiring information about the total number of activities or intercepts on a particular switch; and

obtaining intelligence information from analysis

of billing records and other business data.

Threats to security originate from both internal

and external sources. Operational components

and connections between the components involved in managing the setup and control of surveillance activities are particularly susceptible to

intrusion. Telephone companies have been favorite victims of “hackers” since telecommunication

networks became “computerized.” Abuses by

hackers have been aimed at switch elements, support billing, and other record-keeping functions.

Notwithstanding the concern for potential outside hackers, the internal security threats from

intentional or careless breaches in security by telephone company employees, or contractors to service providers, may be a greater threat.

There are several categories of security risks:

 Disclosure of Information: Information about a

specific surveillance may be obtained by an unauthorized individual, e.g., that a wiretap is being initiated on a specific target, or information

gathered from the wiretap, might be made

available to an outside individual. Even operational information about the number of surveillances performed at a single switch or within a

service provider’s area is considered to be sensitive information.

 Redirection of Information: There is a risk that

intercepted information might be accidentally

sent to the wrong location, or that it might

intentionally be diverted to another location, or

destroyed.

 Manipulation of Information: Data transmitted

to and received by law enforcement officials

must be reliable. No doubt about its association

with the intercept target and the integrity of the

23 The recent arrest of Kevin D. Mitnick, a well-known and previously convicted computer hacker, for computer crimes, points to the problem confronting computer and telephone networks at the hands of talented and skillful computer criminals. It is alleged that Mr. Mitnick broke

into computer networks and stole files and acquired 20,000 credit-card numbers by tampering with a telephone switch in a cellular service

provider to reroute his calls to evade surveillance. John Markoff, New York Times, p. 1, Thursday, Feb. 16, 1995, John Schwartz, Washington

Post, Sunday, Feb. 19, 1995, p. 1.
24 | Electronic Surveillance in a Digital Age

information can exist if it is to be accepted as

evidence by the Courts. Neither intentional nor

unintentional manipulation or corruption of the

data must occur.

 Destruction of Information: Information used

to control the establishment of surveillance

could be lost or destroyed, resulting in failure

to perform the surveillance.

 Internal Risks from Trusted Personnel: Fraudulent initiation or termination of intercepts, or

disclosure of intercept information.

There are physical ways to protect the integrity

of electronic intercepts, and ways in which databases and records can be protected from tampering (logical means of protection). Physical

protection includes:

 control of information to initiate a wiretap to

prevent unauthorized disclosure;

 restricted access at the service provider’s facility; and

 physical security in the transmission system

and control points outside the carrier’s plant to

prevent unauthorized interceptions.

Logical approaches to protection of data and records include:

 partitioning databases, switch function, peripherals, etc.;

 auditing systems to secure the storage and processing of business records provided to law enforcement agencies in the course of an

intercept;

 controlling access through logging procedures

for entry into the operational components controlling the intercept;

 prohibiting direct remote access through dialin procedures to an operational component involved in an intercept; and

 encryption of data transmitted to the law enforcement monitoring site to prevent access to

the intercepted information in the course of its

transmission from the distribution point to the

law enforcement monitoring site.

FINDINGS AND OBSERVATIONS

The Communications Assistance for Law Enforcement Act was approved on October 25, 1994.

The act is currently in an early stage of organization, planning, and implementation. Few conclusions can be reached on a cursory examination of

the progress made over the short period of observation. Nevertheless, a few indicators are

worth noting:

 General Observation: Although the technical

complexity of modifying the existing network and designing features into new

technology that will meet law enforcement’s

electronic surveillance needs is not trivial,

the industry is highly competent and capable of meeting the technical challenges. If

major problems arise in meeting the needs of

law enforcement, they will likely arise as a

result of institutional difficulties in dealing

with a diverse, highly entrepreneurial industry made up of a large number of telecommunications companies offering many

new innovations and features, with the number of players steadily increasing.

 Timing: There is a possibility that the complexity of re-engineering and modifying the

technology installed in the current telephone network to meet Law Enforcement’s

needs may exceed the time allowed for compliance by the Act.

The Attorney General is to notify the carriers of

the “actual and “maximum” capacities by October

25, 1995 required to meet law enforcement’s requirements to bring the carrier’s technology up to

specifications. The carriers must then respond to

the Attorney General’s notification with statements of their ability to meet the capacity and capability requirements within 180 days. Carriers

then have three additional years (four years after

approval of the Act) to comply with law enforcement’s requirements (October 25, 1998).
Chapter 1 Summary and Discussion | 25

If the Attorney General fails to meet the October 25, 1995 deadline for publishing Law Enforcement’s capacity notice, then the service

provider’s compliance will be delayed accordingly. If the carriers decide that law enforcement’s requirements are not reasonably achievable within

the allotted time, they can petition the FCC for an

extension of up to two years. This would push

back the required compliance date to as late as October 25, 2000.

There remains a question as to whether there

will be sufficient time for publishing law enforcement’s capacity requirements, completing the ongoing consultative process between the industry

and Law Enforcement, providing accredited standards bodies with specific input needed to meet

Law Enforcement’s requirements, completing the

process leading to accepted industry standards or

collaborative solutions as well as allowing time

for switch manufacturers to engineer and develop

the modifications, and manufacturing, delivering,

installing, and debugging the switch modifications.

Once a clear set of generic specifications is

available, it generally requires two years to develop the software and hardware to implement a complex set of new features. Simple modifications

may require less time. Adjustment and debugging

of supporting software and operating procedures,

including revising security procedures within the

carrier’s operations, may require considerable

time and involve a high level of uncertainty.

The above holds true only for conventional

telephone switches in the service provider’s central office. Advanced Intelligent Networks (AIN),

which operate interactively with software-based

computer systems present more complex problems and a higher level of uncertainty about the

seamless operation without service interruption.

As with any software modification, those for AIN

systems are complex, sometimes tricky, and in the

worst case, can bring down a network if there is a

malfunction (malfunctions of this nature are not

specific to AIN, but their complexity makes them

more vulnerable).

Cellular systems present complex operational

problems to handle all hand-offs to other carriers,

etc. New modes of transmission, e.g., PCS, provision of telephone service by cable television companies, and Asynchronous Transfer Mode (ATM)

fast-packet networks are future technologies that

will allow time for further development without

hindering Law Enforcement’s mission.

 Security: The installation of technologies to

meet law enforcement’s requirements will

place new demands on carriers to ensure the

security of the intercepted information and

of the network at large.

Security of the telephone system is a more serious problem than news accounts suggest. There is

a concerted effort by the telephone companies to

play down security breaches, but many more have

occurred than the public is aware. Anecdotal evidence in the possession of the carriers indicate that

communication networks (even the Department

of Defense) have frequently been penetrated by

hackers. By using debug routines and “spoofed”

passwords (to mimic those with legitimate privileges) hackers have been able to extract passwords

and personal identification numbers, to make

fraudulent calls and illegal transactions. Others

have maliciously altered databases or extracted

personal information that they were not authorized to have. Allegedly, there is a black market

for surveillance, where clever hackers can establish surveillance of individuals from outside the

system. Though publicly unconfirmed, there have

been accounts of suspected incidents where hackers have even intercepted law enforcement communications, including the contents of wiretaps,

although it is highly unlikely that this has occurred given the complexity of taking such action.

In other instances, intercepts may have been disconnected from the outside through software

switches. It is also possible for hackers to determine who is being tapped, which could be of value

to the criminal element.

Not all of the security problems originate from

the outside. There have been occasions where tele-
26 | Electronic Surveillance in a Digital Age

phone personnel, or manufacturers/vendors technicians, who know the system and have access

from the inside, are motivated to make fraudulent

use of information obtainable from computerbased databanks.

The security requirements of P.L. 103-414 will

require the industry to tighten its supervision over

information regarding the existence of a wiretap

and the identification of those who are tapped.

Furthermore, the content of the intercepted calls

will require protection, since law enforcement listening (monitoring) posts may be some distance

from the tapped switch (linked by leased or private

lines), with opportunities for others to modify or

obscure the contents or otherwise diminish its integrity as evidence.

 Safe Harbor: The government may have to

make an affirmative declaration that an

“adopted” industry standard or technical

requirement is sufficient to satisfy the “safe

harbor” provisions of the Act.

Section 107(a) of the Act provides that if equipment to meet law enforcement’s requirements is

built to meet “publicly available technical requirements or standards adopted by an industry

association or standard-setting organization,”

vendors or service providers will be considered in

compliance with the Act if the standard or technical requirements meet the requirements of Section

103 of the Act. If standards are accepted by an accredited standards-setting organization, the clear

meaning of the Act would protect carriers and

vendors from charges of noncompliance. However, the Act is ambiguous with regard to what

constitutes “adopted by an industry association.”

Standards certified by an accredited standards organization go through formal processes and orderly steps of approval before being certified as a

standard. “Industry associations,” without standards-setting functions, on the other hand, may

have no formal approval process and operate

loosely by consensus only.

The Electronic Communication Service Providers Committee (ECSP) is the primary industrywide body that has dealt with the requirements of

the Act. ECSP is sponsored and provided administrative support by the Alliance for Telecommunications Industry Solutions (ATIS). The ECSP is

not an accredited standards setting body as generally recognized. However, ATIS does sponsor other recognized standards setting bodies (T1,

Protection Engineers Group (PEG), Standards

Committee 05, etc.). Within the ECSP, only the

Cellular Action Team and the Personal Communication Action Team are coordinating their work

on electronic intercept solutions through accredited standards organizations.24

The ECSP committee, however, is only one of

many possible industry groups with the expertise

to develop technical requirements. Any industry

organization that tackles the task would be expected to include the involvement of the of the

FBI’s Telecommunications Industry Liaison Unit

(TILU) in its deliberations to ensure that its standards meet the capability requirements of Section

103 of the Act.

Whether a general consensus reached by ECSP

participants or any other industry organization on

technical requirements would constitute “adopted

by the industry” in meeting the requirements of

the Act is unclear. Industry participants in ECSP

have raised questions regarding the official status

of the work produced by the Committee. Thus far,

the government has not responded to industry’s

concerns in a definitive way.

If the industry fails to issue technical requirements or standards, or if it is believed that the technical requirements are deficient, the FCC is

empowered to establish such requirements or

standards if petitioned to do so by any person or

entity. This process could be used by anyone, including law enforcement agencies, to petition the

FCC to establish an adequate standard.

24 The Standards Organization for Cellular Technologies is designated TR45. TR46 covers PCS technologies. Both standards groups operate under the aegis of the Telephone Industry Association (TIA).
Chapter 1 Summary and Discussion | 27

Continued uncertainty about what constitutes

an “adopted” industry technical requirement

could result in future litigation to decide the question should a cause of action arise. To avoid the

prospect of future litigation and possible delays,

the government might consider a certification

process for standards or technical requirements

that would assure the industry that a technical requirement that is developed by consent of a nonstandards-setting association would provide them

with a safe harbor from sanctions for noncompliance.

One option might be to use the authority provided the FCC for establishing standards under

Section 107(b). Association-approved technical

requirements (absent an accredited standard)

could be referred to the FCC for evaluation and

formal adoption.

 Cost Reimbursement: If the Act is to achieve

its intent with regard to upgrading law enforcement’s ability to intercept electronic

communications in the existing network

(equipment installed prior to January 1,

1995), then Congress must appropriate sufficient funds (and the Attorney General

must make them available to the service providers) to offset the costs of retrofitting. Reliable cost data for detailed fiscal planning

will likely not be available until the budget

period for fiscal year 1996.

Reliable engineering and operational cost estimates cannot be made until after the Attorney

General issues the capacity requirements that the

individual service providers must meet to comply

with the Act. At the time of this report (spring

1995), there have been no decisions on the

technology needed to meet the capabilities for

electronic surveillance required by the law enforcement agencies. Furthermore, the capacity

and specific geographical priorities for implementing the Act are not scheduled for release until

fall of 1995.

Failure of the government to appropriate and

expend adequate funds to pay the carrier’s expenses for complying with the act will automatically place the carriers in legal compliance with

the act (for equipment installed prior to 1995), but

would not result in the deployment of the technology needed by the law enforcement community in

the timeframe set forth in the Act.

In the event that sufficient funds are not appropriated for the purpose of offsetting the costs to

carriers for retrofitting pre-1995 equipment, the

rate of replacement of existing equipment with

new equipment that would be required to meet law

enforcement’s capability requirements would depend on the business plans of the individual service providers. Such plans could depend on

market strategies, age and condition of the service

providers equipment, development of new

technologies, tax consequences, etc. This could

result in spotty and uneven deployment of new

equipment, with the capabilities and capacity to

meet the Act’s requirements (islands of capability), located among service areas of other providers

that continue to operate old equipment that does

not comply with law enforcement’s requirements.

The General Accounting Office (GAO) is mandated by the Act to compile cost estimates in a report from the Comptroller General that is due

April 1996 and every two years thereafter. The

GAO report is to include “findings and conclusions. . .on the costs to be incurred by telecommunications carriers. . .including projections of the

amounts expected to be incurred and a description

of the equipment, facilities, or services for which

they are expected to be incurred.” (Sec.

112(b)(2)).

 Future Technologies: Law enforcement

agencies will continually face challenges in

maintaining their electronic surveillance

capabilities in the future as new communications technologies and services are developed.

The field of communication technology is developing rapidly. A stream of new technologies

are qued to complement, compete, or displace the

communications systems of today. Computerbased packet communications systems, satellitebased global communications, and the interconnection of virtually every form of electronic

communication system through a National In-
28 | Electronic Surveillance in a Digital Age

formation Infrastructure (NII) will require law enforcement agencies to keep abreast of these

developments as they come online. Along with

the technological challenges that future systems

will bring, are institutional and international issues that must be addressed as global communication systems are developed.
Technical

 Aspects of

 Electronic

 Surveillance1

he evolution of the modern telephone system, from its invention in 1876 followed a predictable path of development until digital technology and optical fiber began

seriously supplanting analog technology and copper wire

in the U.S. telephone system. Since about the 1970s the technology of electronic switching, digital processing, computer architecture, and optical transmission have progressively developed into

commercial devices and applications whose low costs and broad

capabilities have made these technologies the foundation of a new

era of communications.1

The speed with which the nation’s communication system is

shifting from a wire-based analog system to digital computercontrolled switches and optical fiber is astounding. In 1989, nearly one-half of the major telephone companies’ switches were

digital. By 1993 the proportion of digital switches had grown to

80 percent.2 Fiber optic transmission systems also are rapidly displacing copper in local service and long distance carriers. In 1985,

long distance carriers had about 20,000 miles of fiber optic cable

in service. By 1993 the long distance companies reported slightly

1 Material in this chapter was synthesized from documents prepared by the various

action teams of the Electronic Communication Service Providers (ECSP) committee, operating under the aegis of the Alliance for Telecommunications Industry Solutions

(ASIS). The OTA project director for this report attended the functions of the ECSP under

a nondisclosure agreement. The material herein contains no information considered to be

sensitive by the law enforcement agencies, or proprietary by the industry personnel reviewing the draft document.

2 Testimony of A. Richard Metzger, Jr., Deputy Chief, Common Carrier Bureau, Federal Communications Commission, before the U.S. House of Representatives, Committee

on Energy and Commerce, Subcommittee on Telecommunications and Finance, Sept. 13,

1994, 103d Cong., 2d sess.

| 29
30 | Electronic Surveillance in a Digital Age

more than 99,000 miles of optical fiber.3 Local

telephone companies had about 17,000 miles of

optical fiber installed in 1985, and this grew to

over 225,000 miles by 1993.4

The recent explosion of wireless communication has extended mobile service to more than 734

metropolitan and rural service areas. These service areas geographically overlay the wired

telecommunication systems to which they interconnect. Currently, there are over 1,100 cellular

switches in operation in the United States.5 The

growth of wireless communication has been remarkable. Today, there are more than 16 million

cellular subscribers, and the cellular industry estimates that subscribership will double by 1998.6

Following behind is the next generation of wireless services, the new Personal Communication

Services (PCS), which are similar in function to

today’s cellular communication services, but new

PCS entrants may develop entirely new services

in the future, which could present different problems to law enforcement agencies. Coming next

will be satellite-based communications systems

for personal communication that could extend

wireless communication to nearly every quarter of

the world.

In addition, a convergence of digital and analog

technologies is bringing other nontraditional sectors of the communication industry into what once

was the domain of the telephone companies. Government deregulation and industry restructuring

has the potential for further blurring the business

lines between the cable television industry and

the telephone carriers, and has raised the prospect

that electrical utilities might someday be competitors in the telecommunications market as

well.7

Through the 1950s and into the 1970s law enforcement’s wiretap requirements were easily

met. The nation’s telephone system largely consisted of twisted copper wires that connected subscribers to central office switches that routed the

calls to their destinations through copper cables or

overland via microwave radio, and later satellites.

The transmitting and receiving instruments were

commonly used telephones. Business may have

had Private Branch Exchanges (PBX) to route

their calls. But in general, it was a comparatively

simple system of wires connected to switches that

connected to other wires that routed the calls to

businesses and residences. Law enforcement officials, armed with the necessary legal authorization, would simply physically connect “alligator

clips” to wire terminals and monitor the contents

of calls coming to and going from the telephone

line authorized in the wiretap order. (See figure

2-1.) Since much of the system was under the control of American Telephone and Telegraph

(AT&T), although GTE and other independent

telephone companies operated as well, the national system was largely based on the same standards, operating protocol, and equipment design

used by AT&T.

In the recent past, additional complexities were

added to the system when transmission technologies for the copper-based analog system were developed to provide more bandwidth, and hence

speed, to handle larger volumes of calls. A transmission mode referred to by its industry standards

name, “T1,” and a faster version “T3,” which was

originally developed for intrasystem high-speed

trunking, became available for high-volume users, largely businesses.

3 Federal Communications Commission, Fiber Deployment Update, table 1, May 1994.

4 Id at table 5.

5 Testimony of Thomas W. Wheeler, President and CEO, Cellular Telecommunications Industry Association, before hearings of the U.S.

House of Representatives, Committee on Energy and Commerce, Subcommittee on Telecommunications and Finance, Sept. 19, 1994.

6 Cellular Telecommunications Industry Association, “The Wireless Factbook,” p. 36, spring 1994.

7 James Carlini, Telecom Services, “Utilities are Hungary for a Piece of the Action,” Network World, p. 55, Sept. 19, 1994.
Chapter 2 Technical Aspects of Electronic Surveillance 131

Central

office

tandem

Local

exchange

switch

SOURCE Off Ice of Technology Assessment, 1995

This technology gains its speed by separating

the electronic signal into discrete segments divided sequentially in time (Time Division Multiplex, or TDM) and routing them sequentially over

the line to be resequenced at the receiver (demultiplexed). In this way the signals are virtually routed

over channels so that many more bits of information can be transmitted over the wire or coaxial

cable at the same time.

Multiplexing can increase the normal speed of

transmission from thousands of bits per second

(kbs) to 1.544 million bits per second (Mbs) for

T1 and 45 Mbs at the T3 rate. Because multiplexing breaks the continuity of the signal in the transmission phase, it places an additional degree of

difficulty for electronic surveillance. Also, since

1984, long distance carriage has been separated

from the local exchange carrier, so that now an intercepted call might flow among several different

carriers on its way to or from a target. (See figure

2-2.)

The current telecommunication environment is

considerably more complex. Wireless technology

has expanded the reach of the telephone system.

The combination of digital transmission, imbedded computer databases, digital switching,

and the increased speed of optical fiber cables provide many more functions, options, and flexibility. As a result, many of the functions and

operations, which were once the sole province of

the telephone operating companies, are now performed directly by the subscriber, sometimes

without the knowledge and control of the carrier.

Wide-area centrex operations, for instance, allow

a large business subscriber to manage a communication system within the carriers network, but

independent of the carrier with regard to assigning

internal number, call routing, and location identification-a virtual network within the carrier’s

network. Wireless subscribers may roam outside

their home service area. Features such as call forwarding, speed dialing, call transfer, and specialized high-speed computer-based services add

complexity to the problems of wiretapping for law

enforcement agencies. (See figure 2-3.)

The future operating environment will contain

several additional actors than are now present in

the telecommunication network. Personal communication service providers (PCS) will extend

the reach of wireless communication adding more
20 I Electronic Surveillance in a Digital Age

SOURCE Federal Bureau of Investigation, 1994.

mitted to a designated law enforcement monitoring facility. However, access to the intercept will

be controlled by the service provider and not the ■

law enforcement agency. Transmission of intercepted communications must satisfy the following guidelines: ■

■ Where call setup information and call content

are separated during interception, the service

provider must take steps to ensure accurate

association of call setup information with call

content.

Transmission of the intercepted communication to the monitoring site must be made without altering the call content or meaning.

Law enforcement agencies require that the

transmission facilities and formats of the information transmitted the monitoring stations

be in a standard form.
Chapter 2 Technical Aspects of Electronic Surveillance 133

Business

SOURCE Federal Bureau of Investigation, 1994

limited by the imagination of the systems engineers and developers and the acceptance of the

new applications in the marketplace. Faster transmission systems and computer networking will

lead to advanced systems that can leverage the

bandwidth into currently unforeseen applications.

The vision of a National Information Infrastructure (NH), if realized, could unleash a diversity of

new services based on computer mediated multimedia communication far different from the current communication paradigm. A diverse offering

of features and services is currently available on

the U.S. telephone network, and this list will grow

as time passes. (See table 2-1.)

TECHNOLOGIES

Each of the technologies or features listed in table

2-1 requires a technical modification or solution

to meet the requirements of the Act. Some solutions may be easily achieved through software

programs or minor hardware modifications. Other
34 I Electronic Surveillance in a Digital Age
Chapter 2 Technical Aspects of Electronic Surveillance | 35

modifications will require redesign or re-engineering, or perhaps significant development efforts to meet law enforcement’s needs. Some of

the technologies listed in table 2-1 are already

deployed throughout the national system. Others

are installed or offered by some service providers

and not by others, and sometimes carriers may be

using different (incompatible) standards to drive

or manage the same generic technology. Still other

technologies are just emerging into a commercial

stage of development and have not yet been widely adopted or deployed by the industry.

One such developing technology is the Asynchronous Transfer Mode (ATM) of transmission,

which is considered by many in the telephone and

computer networking industry to be the chosen

technology for building the backbone of the next

generation of telecommunication networks. This

technology would radically change the characteristics and operation of the network by integrating

voice, video, and data into the operating system. It

offers phenomenal speeds (rate of information

transfer), potentially up to billions of bits per-second range (gigabits). ATM is able to carry traffic

originating from many different kinds of networks

that will make up the National Information Infrastructure of the future.

Other digital network technologies are based

on the transmission of information packets

(frames or cells) that route segments of the information string (a voice message, an image, or

data) to individual addresses within the interconnected network in a so-called “connectionless”

mode. This is the transmission mode used on the

Internet. Packets for an intended recipient may

take a number of different routes to reach a destination, depending on the traffic congestion on

the network and other network management factors.

Each new technological development presents

the industry and law enforcement with a challenge

to maintain parity for electronic surveillance in a

fast-changing communication environment. The

combined efforts and collaboration of the industry

and the law enforcement agencies will likely be

required on a continual basis for the foreseeable

future as the nation’s communication infrastructure undergoes a nearly complete metamorphosis.

The industry/government joint activities within the Electronic Communication Service Providers (ECSP) committee discussed in chapter 1 is

addressing the practical matter of adapting the

telecommunication industry’s installed equipment base to comply with the Act. This, in its self,

is a substantial and expensive task, but the technological challenges presented by the emerging network technologies, and technologies still in a

conceptual stage, will be waiting to be solved

when the immediate task is finished.

The ECSP committee has divided the technologies of immediate concern, i.e., switch-based

solutions, advanced intelligent networks (AIN),

mobile cellular communications, and personal

communication services (PCS). The action teams

are supplemented by others that deal with the interfaces between the carriers equipment and the

law enforcement agencies, and one that considers

the implications of future technological developments.

SWITCH-BASE SOLUTIONS

The function of a switching system is to interconnect circuits. It is the preferred point of access for

electronic surveillance by the law enforcement

agencies. A switch-based solution is an approach

to meet law enforcement’s electronic surveillance

requirements using the traditional central office

switch as the point in the network where access to

the intercept target’s communication is achieved.

There is estimated to be more than 20,000 landline switches installed and operating in the United
Feature/technology Description Feature/technology Description

Call Forwarding

Serial Call

Forwarding

Speed Dialing

Three-Way Calling/

Call Transfer

Calling Line

Identification

Voice-Activated

Calling

ISDN-BRI Access

Loop

Ability to redirect a Directory Number (DN) from

one destination to another Directory Number.

Ability to redirect a call multiple times.

Ability to establish and dial pre-selected numbers

with an abbreviated code.

Ability to add a third party to an on-going call.

The party initiating the service can drop off, thereby transferring the call.

Ability to include calling line identification in call

set-up information.

Ability to use voice commands to dial pre-seIected numbers. (Under development).

Basic rate Integrated Services Digital Network.

Digital Loop Carrier (DLC)

and Fiber-in-the Loop

private Virtual Network

Voice Mail (E-Mail)

Electronic Mail (E-Mail)

Facsimile Mail

Switched Multi-Megabit

Services (SMDS)

High Bit-Rate Digital Subscriber Lines (HDSL)

w

These systems connect subscribers to the

serving end offices. These technologies af- C D

- .

feet traditional techniques for intercepting

communications on the local loop.

A set of software-defined functions that give

a subscriber control of a portion of the bandwidth and switching fabric of a service pro- >

vider that allows the subscriber to manage

that segment of the network as if it were its

own.

Voice mail services provided by a carrier using a peripheral component to switch or an

Advanced Intelligent Network (AIN) platform.

Public E-Mail services offered by common

carriers.

Ability to send a FAX to a mailbox (storage

location) with an associated Directory Number (DN). A recipient can access and retrieve the FAX at a later time.

SMDS is a high bit-rate (fast) connectionless,

cell-relay digital transport service used for

date, voice, and images.

A technology that builds on the ISDN basic

rate that are designed for transport service

used for date, voice, and images.
ISDN-PRI

CLASS Features

Primary rate Integrated Services Digital Network. Asymmetrical Digital Subscriber Lines (ADSL)

Automatic Recall, Selective Call Forwarding, Intelligent Networks and AdCaller ID, Call Blocking, etc. vanced Intelligent Networks

(AIN)

Advanced Intelligent AIN is a platform that supports advanced call

Networks (AIN) features and applications.

Intelligent Customer Premises

Equipment (CPE).

Cellular Ability to provide telecommunications services to Universal personal Telecommobile subscribers using cellular systems. Fea- munication Service (UPT)

tures include intra-system roaming, inter-system

roaming, seamless roaming, and Cellular Digital

Packet Data.

Personal Allow access of services from different locations,

Communications while in motion, potentially on a global basis,

Services (PCS) through satellite communication.

An application of ISDN that provides 1,544

Mbs line speed toward the user and only

64kbs toward the network, hence the reference to “Asymmetrical. ” The standards was

primarily aimed at the delivery of video to the

home (e.g., Video Dial Tone).

Advanced networks based on common

channel signaling using the international

Signaling System 7 (SS7) standard that provides out-of-band, packet-switched communication among network elements. This allows central offices to query databases in

the Service Management System (SMS)

about the called or calling number and subscriber profile information.

Intelligent functions (computer-based built

into modern CPE may interact with non-standard switches, i.e., proprietary electronic terminals, etc., that make interception of signaling information more difficult.

A service that allows a user to access services from any terminal wherever he or she

might be on the basis of a personal identifier.

Those services that the user is qualified for

would be available from wherever the person

might be, The user’s service profile could

therefore be altered from remote locations by

the user.

o

SOURCE Electronic Communications Service Provider Committee (ECSP).
38 | Electronic Surveillance in a Digital Age

States today.8 Approximately 1,200 of these

switches are of a special kind that support Integrated Services Digital Networks (ISDN), a channelized communication mode that serves the

needs of some business customers and a fewer

number of residential subscribers with special

needs. ISDN separates the signaling information

from the call content information, which increases

the speed and flexibility of communication. It also

increases the complexity of wiretapping. Integrated Services Digital network switches are being considered as part of the Switch-Based

Solutions Action Team.

❚ Switch Technology

The 20,000 switches in service today are a mixture

of old and new technology. A few rural areas still

have vintage 1900 step-by-step (SXS) electromechanical switches in their networks, although they

are being quickly phased out. Some electromechanical crossbar switches from the late 1930s

still exist on the network. The electromechanical

switches remaining pose no problem to law enforcement because their technology is simple,

they are largely located in rural areas, they do not

provide flexible calling features, and they are being replaced by modern switches rapidly.

Modern electronic central office switches are

able to provide a vast number of switch features

and services. Electronic switches are based on either analog or digital technology. Analog Stored

Program Control Switches (Analog-SPCS) were

introduced in the mid-1960s, and became the

mainstay for metropolitan switches in the 1970s

and ‘80s. A large number of Analog-SPCS remain

in service, but they are being replaced by digital

electronic switches. Digital-SPCS were introduced in the early 1980s. There is a large number

of Digital-SPCS in the national network, and their

number is growing. These electronic switches are

largely manufactured by four manufacturers:

AT&T, Ericsson, Northern Telecom, Inc., Siemens Stromberg-Carlson.

A number of other type switches provide functions and services in addition to the circuit

switches listed above. These include Packet

Switches, Private Branch Exchanges (PBXs),

Broadband Switches, Cellular Switches, and Personal Communication Services (PCS) switches.

Among the ECSP Action Teams, Cellular and

Personal Communication Services are being dealt

with separately from Switch-Based Solutions in

the central office. On balance, Packet Switches,

PBXs, and Broadband Switches, while they will

be more important in the future, do not figure as

prominently in the network at this time, thus they

present a lesser immediate practical problem for

law enforcement, and are not directly addressed in

the Act.

There are two major categories of switches: local and tandem. A local switch connects one customer’s line to another customer’s line, or to a

connection (trunk) to another switching system. A

tandem switch connects trunks to trunks. A third

category of switch—remote switches—are local

switches where a portion of the switch and some

switch software is located away from the main or

host switch. Host switches can serve several remote switches, and are connected to the remote

switches with connection links. Electronic surveillance at the central office switch will involve

local and tandem switches, as well as host and remote switches.

The major impact that new switching technologies have had on the network is the emergence of

remote digital terminals and switch modules that

terminate the conventional analog interface nearer

the customer and use a digital interface to other

network components.

8 Testimony of Hazel E. Edwards, Director, Information Resources Management/General Government Issues, Accounting and Information

Management Division, U.S. General Accounting Office, before a joint hearing of Subcommittee on Technology and the Law, U.S. Senate, and

the Subcommittee on Civil and Constitutional Rights, Committee on the Judiciary, U.S. House of Representatives, Aug. 11, 1994, p. 5.
Chapter 2 Technical Aspects of Electronic Surveillance | 39

❚ Features and Functions

Introduction of Analog-SPCS into the national

telephone network nearly 30 years ago brought

many new features and functions to customers.

These features (Custom Calling Services) included Call Forwarding, Speed Calling, Call

Waiting, etc. Since that time, hundreds of more sophisticated specialized services have been developed as Digital-SPCS came on line. Many of these

have presented substantial challenges to law enforcement agencies’ ability to conduct court-ordered electronic surveillance.

The features or functions described below present the most significant challenges to meeting the

needs of the law enforcement community:

Call Forwarding

Allows a subscriber to redirect the incoming calls

by dialing the call forward activation code followed by the directory number to which the calls

are to be forwarded. This feature can be activated

and deactivated at any time from the subscriber’s

telephone set.

Electronic switching systems have the ability

to redirect an incoming call to either another directory number within the same exchange, or to

another exchange over a trunk line. When a call is

redirected by the switch, the call content is not

transmitted to the subscriber’s line, but instead is

rerouted at the switch.

Speed Calling

Permits the subscriber to link a set of abbreviated

directory numbers (i.e., one number or two-number sets on the telephone) to the directory numbers

(DN) of frequently called parties at the subscriber’s own initiative. This allows the subscriber to

initiate a call by dialing the abbreviated one or

two-digit number. Activation of Speed Calling is

at the central office switch without involvement of

the service provider. Some versions of speed dialing services permit the subscriber to change the

assignment of directory numbers in real time, i.e.,

in the course of a call, or to change the number assignment remotely. Abbreviated Speed Calling

codes created by the subscriber are accessible to

law enforcement agencies from the local exchange carrier.

Three-Way Calling and Call Transfer

Enables a subscriber to add additional parties to a

call that is in progress. When Three-Way Calling

is invoked, the calling party or the called party

temporarily suspends the conversation, initiates

service and connects to another party, then adds

the new party to the initial call. Call Transfer behaves somewhat as Three-Way Calling, but it allows the initiator of the transfer to drop off the call

while the remaining parties continue the conversation.

Custom Local Area Signaling Service

(CLASS)

Is a set of call management features that provides

the called party with control over incoming calls.

CLASS features are available through both Analog-SPCS, and Digital-SPCS that are equipped to

support the Common Channel Signaling/Signaling System-7 (CCS/SS7) capabilities. CLASS

features place more of the control of the call in the

hands of the called and calling parties. Those features, which provide the called party more control,

generally are enabled by passing the calling

party’s number to the terminating switch as part of

the SS7 call setup message. About a dozen features are available through CLASS services.

Automatic Recall allows the user to activate a

procedure by dialing a code, e.g., *69, that automatically redials the last incoming call—whether

or not the call was answered—without having to

know the caller’s number.

Selective Call Forwarding enables a customer

to define a list of telephone numbers and assign

each a forward-to destination number. Incoming

number on the list are forwarded to the assigned

destination number. Selective Call Forwarding,

and some of the other CLASS features, provide

the customer with the ability to create, modify, activate, and deactivate screening lists at will without the involvement or knowledge of the service

provider.
40 | Electronic Surveillance in a Digital Age

Number Portability

Number portability will allow telecommunications users to retain their telephone numbers over

time, despite moving to different service areas and

physical addresses. Potentially, users could be assigned a lifetime phone number. The telecommunications industry is also developing services that

use a nongeographic number to identify a subscriber, such as AT&T’s Follow Me service. Callers can be reached at the number regardless of

their physical location or the type of terminal

equipment used (i.e., home telephone, office telephone, cellular terminal). The infrastructure to

support these types of services will be deployed

over the next several years.

The availability and use of portable and nongeographic numbers may have several implications for law enforcement. Law enforcement will

have to be able to determine the carrier serving the

investigation target, that person’s location, and

any subsequent carriers and locations involved in

transmitting the communication. Network-based

capabilities to support lawfully authorized interceptions should be capable of providing dialed

number information as well as translated numbers

used by the network for routing calls to or from the

intercept subject.

Integrated Services Digital Network (ISDN)

ISDN provides a broad range of voice, data, and

image services based on digital communication

for transport and control within the network.

ISDN is based on combinations of 64 kbs (thousand bits per second) channels (lines) combined to

increase bandwidth, and therefore increase the

speed and capacity of transmission. Information is

converted into digital form within the subscriber’s

equipment before being ported to the network.

Since everything is in digital form, all voice and

nonvoice information looks the same as it passes

through the system.

ISDN uses a separate 16 kbs digital channel (Dchannel) for signaling, i.e., communication between the subscriber and the local switch. The

D-channel is part of the access line, but it can be

used to carry user-to-user information (e.g., packet messages) as well as signaling information.

The subscriber controls the service features by

sending messages to the switch, and the switch responds with messages to the subscriber over the

D-channel.

The functions and signaling for ISDN are processed through a number of standard interfaces that

provide different data rates (i.e., speed and capacity). The two most common, and of most concern

to the law enforcement agencies, are:

 Basic Access—composed of two 64 kbs Bchannels (for voice, data, or images) and one 16

kbs D-channel for signaling; and

 Primary Rate—operates at a rate of 1.544 Mbs

(million bits per second), composed of 23 Bchannels of 64 kbs each, and one 16 kbs Dchannel for signaling.

With ISDN the subscriber’s signals for activating or deactivating a feature is carried over a separate channel (D-channel) instead of being carried

over the same channel as the call content, as is the

case for Analog-SPCS. Traditional analog intercept techniques are not compatible with ISDN.

❚ Configuration of

Switch-Based Solutions

P.L. 103-414 requires that intercepted call setup

and call content information be instantaneously

available to the law enforcement agency or agencies at one or more monitoring site off the premises of a service provider. Each simultaneous

intercept originating from a switch must be carried individually and be adequately associated

(identifiably linked) with each lawful intercept at

an authorized law enforcement agencies monitoring point. An intercept target may be the subject of

more than one authorized wiretap by more than

one law enforcement agency. In such cases, both

call content and call-setup information must be

routed to both agencies without either knowing of

the existence of the wiretap initiated by the other.

This will require a distribution facility or some

other means to route each intercepted call to each
Chapter 2 Technical Aspects of Electronic Surveillance 141

Intercept

access

point

v

Call content channel

I target & caller

Call data channel

I

Private or

v

SOURCE: Electronic Communication Service Providers Committee, 1995

agencies' monitoring site over a private line or

connection. (See figure 2-5.)

An intercept is initiated by a service provider at

the request of a law enforcement agency having legal authority for the wiretap. The service provider

remains in administrative control of the intercept

through an interface, i.e., a point or connection

common between the service provider’s system

and the law enforcement agencies monitoring site.

Communication links between law enforcement

monitoring sites and the service provider will establish the surveillance parameters for routing information and access to the intercept target’s

speed-dialing lists and automatic call forwarding

lists without direct control of the switch interface

or the distributor component by law enforcement

officials.

Call information, i.e., call content and call data,

is routed automatically from the target line interface within the switch that connects the targeted

line through the distributor component to law enforcement monitoring sites once a lawful wiretap

is triggered by the service provider.

The switch and distribution functions in the intercept configuration shown in figure 2-1 is

straight forward for Plain Old Telephone Service

(POTS), but Integrated Service Digital Network

(ISDN) at the basic or primary rates of service can

carry 2 or 23 calls, respectively. Each channel is

considered to be a separate call, therefores simultaneous processing and routing communications

carried over ISDN, and also multifrequency PBX

trunk lines will likely require more complex solutions.

WIRELESS TECHNOLOGIES

The mobility of an intercept target using mobile

cellular communication presents problems for

electronic surveillance that did not exist a decade

ago. Its flexibility and adaptability for mobile

communication, whether on foot, in a moving ve-
42 | Electronic Surveillance in a Digital Age

hicle, from a boat, or from an airplane, makes it an

attractive alternative mode of telecommunication

for the criminal element.

There are currently two primary modes of wireless, mobile communication available to subscribers: Cellular communications, currently one

of the fastest growing sectors of the telecommunication market, and Personal Communication

Services (PCS), a developing form of wireless

communication with similarities to cellular, but

with differences in operations that may present

unique wiretap problems to law enforcement as

special features are developed. A fourth communication system in the conceptual stage of development uses satellite-based technology for

long-range communications over broad geographic areas. When operational, satellite systems

will increase the complexity of electronic surveillance by the law enforcement agencies, since they

will be capable of transnational and global communication (portending possible problems with

international transfer of information or data). Furthermore, these systems may employ space-based

switching and hand-off technology that places the

control center for communications in remote

reaches of orbital space instead of secure, controlled operation accessible directly on land.

❚ Mobile Cellular Technologies

Wireless cellular service covers 306 metropolitan

areas and 428 rural service areas. Two cellular service providers are licensed to offer service within

each service area. One of the service providers is

the local telephone company serving that area

(e.g., Southwestern Bell for example), and the

second is a non-wireline company (e.g., McCaw

for example). These providers use multiple cell

sites (supra) and one or more mobile switch carriers (MSCs), depending on customer demand. Reseller providers exist, i.e., those who lease and

retail capacity and services from other providers,

but they largely depend on the facilities of the primary service providers.

Cellular service allows a subscriber to move

freely within a defined cellular service area centered around a cell site (each cell ranges between

one and 20 miles in diameter). If the subscriber

moves into an area serviced by a different cell site

that is within the service provider’s service area

(Intrasystem Roaming),9 the call control may be

passed to a new MSC.10 If the user activates the

mobile unit out of his or her home area (Intersystem Roaming), information about the user (MIN,

ESN, authorized services, billing, etc.) is exchanged between the original (home) service provider’s Home Location Register (HLR) and the

Visited Location Register (VLR).

The main elements of a cellular network include:

1. cell sites that provide the radio frequency link

between the mobile user and the cellular network; and

2. Mobile Switching Center (MSC) that performs

call switching and routing, and external connections to other networks (e.g., local exchange

carriers and interexchange carriers). (See figure

2-6.)

Each cell antenna facility is connected either by

wireline or microwave radio to the MSC.11

Cellular radio communication may be either

analog or digital. The radio components of most

of today’s cellular networks are analog-based, but

many of the carriers are slowly switching from

analog systems to digital systems in order to increase the capacity, offer a wider choice of services, reduce fraud, and improve security.

9 The term “roaming” generally applies when the subscriber initiates or receives a call in other than his or her home area.

10Roaming within the service area of another service provider is contingent on the home cellular provider having entered a “roaming agreement” with the second carrier. Roaming privileges are not uniform and reciprocal among all providers.

11 Some rural cellular companies’ may not own a MSC switch, but instead may lease the use of an adjacent cellular companies switch. In this

case the leasor service provider would have control of the switch, and any intercepting activities would have to be performed by the leasor

although an authorized wiretap may be served on the leasee. This problem may need to be addressed by promulgating regulations.
Chapter 2 Technical Aspects of Electronic Surveillance 143

Remote

mobile

switching

center

SOURCE Electronic Communication Service Providers Committee, 1995

Frequency Modulated (FM) radio channels are

currently used for voice communication and control (call supervision and handoff) 1

2 from the subscriber telephone to and from the receiving radio

at the cell site of the service provider. Control

channels relay control information between the

MSC and the mobile unit. Control channels are

used during call setup to transmit dialed digits and

the mobile unit’s Mobile Identification Number

(MIN) and Electronic Serial Number (ESN).

The analog signal received at the cell site is

converted to digital form and transported to MSC

over multiplexed channels of T1 or T3 land lines

or digital microwave radio systems. The multiplexed signals contain voice or data communication, and information about the user (e.g., MIN

12 “Handoff’ occurs when a subscriber travels from one service area to another while a wireless call is in progress.
44 | Electronic Surveillance in a Digital Age

and ESN) and the dialed digits (Directory Number) needed to complete the call.

Once a call has reached a MSC, the connection

to its destination is handled as any call placed on a

land line through a local exchange carrier end office. Based on the number called, the MSC connects the caller through:

 a wireline local exchange carrier switch;

 an interexchange (long distance) carrier point

of presence (a connection point between long

distance carriers and the local exchange);

 a MSC outside the service provider’s service

area; or

 another mobile subscriber within the same

MSC.

A call may pass through several switches and facilities of many service providers before reaching its

destination.

Although cellular networks are similar to the

line-based local exchanges in some ways, they

function differently in others. In a cellular system,

subscribers control access and selection of services ( e.g., activating, answering, addressing) by

sending and receiving control messages from the

mobile unit over the control channel to the MSC.

The MSC receives and decodes the information

from the control channel, identifies the user ( from

the MIN transmitted by the mobile unit), and activates the services, features, and restrictions

associated with the subscriber’s MIN. After the

preliminary setup information is processed by the

MSC, a connection to the Public Switched Telephone Network (PSTN) is established and the

dialed digit information (Directory Number, etc.)

is relayed to the next switch or connect point in the

PSTN. The MSC then monitors the control channel from the mobile unit and awaits further control

signals that indicate a request for disconnect,

movement to another cell, or activation of a feature, e.g., three-way calling.

❚ Configuration of Cellular Solutions

P.L. 103-414 does not address technologies for intercepting the radio transmission associated with

the operation of a cellular system. The preferred

point of access for a lawful interception by the law

enforcement agencies is at the MSC. The requirements of the law enforcement agencies under the

Act focus on switch-based technology at the MSC

and relational databases that interact with the

MSC.

Some cellular switch manufacturers have developed capabilities within their switches to accommodate some of the needs of the law

enforcement community for lawful intercepts.

The requirement under P.L. 103-414 to support

multiple, simultaneous intercepts may, however,

overtax the intercept capabilities now built into

MSC switches.13 The capacity to accommodate

multiple intercepts is determined by the number of

electronic intercept access ports designed in the

MSC switch. Switch manufacturers are working

on modifications to overcome port limitations,

but in some cases physical limits of space within

the switch will limit the number of access ports

that can be added. Switch design was based on the

anticipated increase in capacity needed for subscriber growth. Law enforcement agencies’ need

for increased capacity for electronic surveillance

was not hitherto considered in switch specifications.

❚ Call Setup Information

As is the case with landline telecommunications,

law enforcement agencies require access to line

information for all completed and attempted calls,

including calls forwarded to another number or

voice mail, unanswered calls, and call waiting

calls. Such information includes: The cellular intercept subject’s Mobile Identification Number

(MIN) and Electronic Serial Number (ESN), and

13 Maintenance ports built into the current generation of cellular switches allow access to information needed by law enforcement agencies.

However, the number of access ports are limited, and information at these ports can only be recovered by manual queries. This limits their usefulness for dealing with handoffs from MSC to MSC, slows the recovery of information, and requires the involvement of several law enforcement officials to implement some cellular intercepts.
Chapter 2 Technical Aspects of Electronic Surveillance | 45

the calling party’s line information when delivered

to the MSC that is being tapped.

Call setup information for calls originated by a

cellular intercept target must include all digits

dialed by the subject (e.g., Directory Numbers,

speed dialing, etc.), billing record information,

and signaling information used to establish or redirect call flow (e.g., activating service features).

During the course of originating a call, signaling

information is carried over the control channel to

the MSC.14 After connection is made with the

called party (cut-through), subsequent dialing information from the target’s mobile unit (e.g.,

pulses/tones representing digits, voice dialing,

etc.), including information generated by the subject in response to system queries, travel over the

bearer channel (call content channel). The call

management information transmitted on the bearer channel is not interpreted by the switch, and

therefore is not available to the law enforcement

agency in the call setup messages. This information is in the form of audible tones or voice information commingled with call content.

❚ Call Content

Law enforcement agencies require access to cellular call content of the intercept target’s terminal,

including voice, voice band data, and paging/

short messages.15 Access to call content must be

provided by the cellular service provider for calls

originated or terminated to the intercept target’s

mobile number, including mobile-to-mobile

calls, mobile-to-wireline calls, and wireline-tomobile calls. All of the custom calling functions

invoked by the subject, e.g., call forwarding,

voice mail, three-way calling, call waiting, etc.,

must be accessible while the service provider

maintains access to the call.

For redirected calls, access is required from the

time that the bearer (call content) channel to the

target (either the primary called number or to a redirected number) is established, until the call to

the forwarded-to target is released. If access to the

communication cannot be maintained, the cellular

service provider is required to provide the law enforcement agency with information that will enable law enforcement to determine the new

service provider’s area, whether landline or cellular. Law enforcement agencies would prefer to

have access maintained by the cellular service

provider for three-way call for the duration of the

call whether or not the intercept subject’s call is

dropped. Industry technicians are not sure that this

is feasible in a cellular system.

❚ Mobility

Cellular service providers are to provide continuous access to all ongoing calls, so long as the carrier maintains access to the call, regardless of the

number of handoffs that may occur, whether intracell, intra-MSC, or inter-MSC. Inter-MSC handoffs include: handoffs within a service provider’s

area when more than one MSC serves an area;

handoffs between different service areas operated

by the same service provider; and handoffs between different service areas operated by different

service providers. The intercept must be maintained regardless of how many intervening handoffs might occur. After handoff, law enforcement

agencies require access to information identifying

the visited service area and the new service provider’s identification so that a lawful authorization (secondary carrier assistance order, which is

derived from the original court authority) for intercept information in the new service area under

the control of the second or successive carriers can

be obtained.

14 Each cellular service provider within a market area is assigned 416 channels for communication. Twenty-one of the channels are control

channels that continuously connect each activated handset with the cellular system.

15 Short Message Service is a function offered by some cellular service provider. It is similar to paging, with abbreviated messages being

transmitted over the control channels.
46 | Electronic Surveillance in a Digital Age

❚ Roaming

When roaming outside of the home service area,

law enforcement requires access to all calls initiated or received by the subject if the visited service provider has received a lawful request to

activate an intercept, and arrangements have been

made for delivery of the information to the law enforcement monitoring site. The visited service

provider has no legal obligation to intercept a cellular target’s calls once the subject moves out of its

service area unless it is a call in process (supra).

The home cellular service provider is required to

provide access to any call setup information or call

content if access is maintained in the home area

during call delivery to a roaming subject.

❚ Registration Information

When a mobile intercept subject roams into a new

service area, activates his or her mobile unit, and

requests service, the home service providers

Home Location Register (HLR) exchanges information with the new cellular service provider’s

Visiting location Register (VLR). When this occurs, law enforcement agencies require information on the identity of the new service area

requesting the registration information. Law enforcement must then obtain a lawful authorization

to access the call content and call setup information from the visited service provider.

❚ Service Site Information

Law enforcement agencies in possession of the

proper Title III court authorized electronic surveillance order (P.L. 90-351, Sec. 801 et. seq.) or an

enhanced pen register16 (but not under law enforcement’s pen register or trap and trace authority) may ask a service provider for detailed service

site information regarding an intercept target’s

location. For example, a carrier provider may be

required to deliver information identifying the cell

site from or to which service is being provided, the

cell sector, or analog radio frequency power levels

coming from the intercept subjects terminal (a

measure of distance from the receiving cell’s antenna), the identity of the service area supporting

communications after a handoff, and other geographic information available, including the subject’s physical location if known.

Cellular Intercept Functions

The functions for intercepting electronic communications in the cellular environment parallels that

used for landline switches (supra), but may require different architectures. However, setting up

a call and managing it in the course of cellular

communications will involve several steps, some

of which are not used in landline switches, e.g.,

activation, registration/deregistration, and call

handoff.

A service provider that controls a subject’s

HLR must identify and somehow set a flag within

the subject’s service profile to indicate that intercept processing is required at the MSC. If the intercept subject is visiting another service area of a

cellular carrier that has been lawfully requested to

initiate an intercept, the visited service provider

may tag the subject (a temporary tag) within the

VRL to indicate that information processing is

needed when the subject activates services within

its area.17

The lawful intercept request to the cellular service provider will typically call for:

 Intercept Subject Identifier (MIN),

 requesting law enforcement agency’s name or

numerical identifier,

 the law enforcement agency’s monitoring location (line or identifier), and

 authorization and access information (e.g., service provider’s personnel authorized to access

or change intercept data).

16 The basic authority for instituting a pen register surveillance is contained in 18 USC 3123. More latitude is granted for pen registers to

obtain more detailed information on a subject is authorized under the procedures set forth in 18 USC 2703.

17 This process is still under consideration by industry and law enforcement agencies.
Chapter 2 Technical Aspects of Electronic Surveillance | 47

Law Enforcement Access

Call setup information, signaling data, handoff information, call forwarding, call waiting, call content information, etc., will be transmitted in real

time, or as soon as possible, to the law enforcement monitoring site. Call setup information (i.e.,

MIN, ESN, called or calling number, date, time,

and available location information) may be transmitted over the signaling channel of law enforcement’s monitoring line.

❚ Personal Communications Service

(PCS)

The Federal Communications Commission (FCC)

is currently in the process of auctioning a 160

Megahertz portion in the 2 Gigahertz band of

spectrum for the development of a new wireless

PCS subscriber service that will perform similarly

to cellular systems and will likely become the next

generation of competitors to cellular services. Service providers have developed conceptual plans

and in some cases have demonstrated PCS systems. However, development and implementation

of such plans are at least two to five years away

from commercial service. PCS, therefore, is at an

immature stage of development that will allow the

features needed for electronic surveillance to be

built as an integral part of new systems.

PCS systems will operate at much higher radio

frequencies (2 Gigahertz) than cellular systems

(800 Megahertz). The higher operating frequency

reduces the distance that a subscriber can be from

a base radio station (cell) and maintain communication. PCS systems, therefore, will consist of

many more smaller cells (microcells that cover a

diameter of up to one mile around the antenna) to

cover an area than is now commonly used by cellular service providers to serve the same size area.

Unlike current cellular systems, PCS systems will

be fully digital, and PCS handsets, will operate at

lower power levels.

The major difference between the features offered by cellular services and PCS is the one-number service to be offered by PCS. A single-number

system allows maximum personal mobility. Under this concept, a single directory number would

be used to direct all calls to a user wherever he or

she is. Cellular systems currently offer a measure

of personal mobility by forwarding calls to a

user’s cellular telephone when they travel. But

this feature operates independently of the Public

Switched Telephone Network (PSTN) landline

system and is only accessible through cellular service providers with databases that track a subscriber’s location. Landline switching routines

were based on having a directory number

associated with a fixed location, not a mobile terminal.

The concept of one-number service (it has also

been dubbed Follow Me) would integrate the

landline network into the switching fabric of PCS

by establishing a nongeographic prefix—500

—in place of the area code. The 500 number

would indicate to the landline carrier that the call

needs special handling to route it to a PCS or cellular carrier.18 To do this, the landline carrier’s Intelligent Network technology (infra) must be

integrated with the PCS and cellular system, all

using common routing databases. Should this level of integration be obtained, a personal handset or

a cellular terminal could be used either as a mobile

instrument, or a substitute for the cordless residential telephone.

PCS is in an early stage of development. There

is considerable uncertainty as to what the standards will be for the industry. Given PCS technology’s stage of development, accommodating the

law enforcement agencies’ needs for electronic intercepts can follow a more logical development

and progression than is possible for either cellular

or landline networks that have an installed techno18 Landline carriers now use a “500” dialing sequence to allow subscribers to use a touch-tone phone to update a database that indicates

where incoming calls should be routed for cellular service. These functions are not integrated into the landline service provider’s switching

system, however.
48 I Electronic Surveillance in a Digital Age

Terminal

Radio personal

terminal (RPT)

SOURCE Electronic Communications Service Providers Committee, 1995

logical base that must be adapted or modified to

comply with the requirements of the Act.

Configuration of a PCS System

The main components of a PCS network are similar to those of a cellular network, although different names are assigned to analogous parts of the

system that perform the same function in each.

The PCS Switching Center (PSC) operates very

much like the Mobile Switching Center (MSC) in

the cellular system. Both serve as a gateway to

connectivity with the Public Switched Telephone

Network (PSTN) and other external networks.

(See figure 2-7.)

The Terminal Equipment (TE), i.e., user equipment, such as a computer or data terminal, can

communicate with the PCS infrastructure in either

a wireless of wireline mode. The Radio Personal

Terminal (RPT), (a lightweight, pocket-size portable radio terminal) directly accesses the Radio

Port (RP) for connecting the user to telecommunications services while stationary or in motion.

The TE may use either Integrated Services Digital

Network (ISDN) or non-ISDN transmission protocols. Wireless access is through Radio Terminations (RT), which terminates voice and data for the

TE and forwards the signal information in digital

form to downstream components, i.e., the PCS
Chapter 2 Technical Aspects of Electronic Surveillance | 49

Switching Center (PSC) for processing. Wireline

access from a TE is linked directly to the PSC.

The Radio Port Controller (RPC) coordinates

the wireless traffic received from the Radio Ports.

It may also control handoff of mobile-to-mobile,

or mobile-to-fixed-location calls placed among or

between users through Radio Ports under its control. The RPC coordinates all calls placed or received by wireless users, and serves as the

gateway to the PCS Switching Center.

The Radio Access System Controller (RASC)

coordinates the functions among the Radio Port

Controllers under its control. It supports the exchange of call, service, and handover control

signaling and the transfer of terminal and user information. The RASC may also perform the internal bookkeeping function of charge recording, as

well as linking with Terminal Mobility Controllers (TMCs), and the Personal Mobility Controllers (PMCs), which manage the terminal

registration, authentication, locating and user/terminal alert functions stored in the Terminal Mobility Data Store (TMD) and Personal Mobility

Data Store (PMD), respectively.

The PCS Switching Center (PSC) performs the

connection control switching functions for accessing and interconnecting outside network systems

to provide end-to-end services. Since PCS systems are designed to provide services to users

based on the user’s personal identity, rather than

on a physical location as does wireline services

(and to some extent cellular services), the PSC

must interact with the PMC (and its supporting

PMD) to access the user’s service profile for registration, authentication, call alerts (ringing), and

call management. The PCS must also have access

to the service limitations and restrictions for a specific user, so therefore it may also have to interact

with the TMC for information about wireless terminals.

A PSC serves five functions:

1. basic call and connection control for access and

interswitch routing,

2. service control for personal communications

users and terminals,

3. switch bearer connections to support handoff

among Radio Port Controllers,

4. mobility management associated with personal

communications users and terminals, and

5. network control and associated interworking

for access to external networks.

The Terminal Mobility Controller (TMC) and

an associated database (Terminal Mobility DataStore, TMD), and the Personal Mobility Controller (PMC) and an associated Personal Mobility

Data-Store (PMD), provides control logic to the

system elements. The TMC/TMD handles authentication, location management, alerting, and

routing to the appropriate RPT/RTs. The PMC/

PMD provides information for personal user authentication, service request validation, location

management, alerting, user access to service profile, privacy, access registration, and call management (routing to destination).

Internal systems functions, e.g., systems monitoring, testing, administering, and managing traffic and billing information, is handled through

Operations, Administration, Maintenance, and

Provisioning (OAM&P) components. Internetworking Functions (IWF) serve to ensure that all

networking technologies work consistently and

seamlessly to provide PCS users reliable service.

The PCS system, like the cellular systems, will

be able to connect with a variety of outside networks that offer a range of services, including

wireline (local and interexchange carriers), cellular, Competitive Access Providers (CAPs), etc.

It is yet uncertain whether PCS will provide

Auxiliary Services. These include voice mail,

paging, short-message service, etc.

Configuration of PCS Intercept Approaches

If all calls to and from a PCS intercept target are

processed by the PCS Switch Center (PSC), with

no calls to or from the target being switched at the

Radio Port Controller (RPC) without first routing

through the PSC, then electronic surveillance for

PCS systems is analogous to the switch-based
50 | Electronic Surveillance in a Digital Age

solutions being considered for cellular and wireline services.

Registration and Activation—The Personal

Mobility Data Store (PMD) and the Personal Mobility Controller (PMC), which store and control

personal service information, can be used to flag

an intercept subject for surveillance. If a home

PCS service provider is requested by a law enforcement agency to implement an intercept, the

intercept subject’s PMD/PMCT entry would be

modified to show:

 Intercept Subject Identifier (personal and/or

terminal number);

 Requesting Law Enforcement Agency;

 Monitor Site Location (line/directory numbers); and

 Authorization and Access Information. This information would be sent to the home service

provider’s TMC/TMD and noted as a temporary intercept request.

Upon receiving a request for services from the intercept subject, the TMC/TMD would activate the

intercept.

In the case that a nonhome PCS service provider that does not have control over an intercept

subjects PMD/PMC is requested by a law enforcement agency to initiate an intercept, the service

provider would enter the subject’s personal service information and intercept information in the

its TMC/TMD. The TMC/TMD would activate

an intercept when a subject requests service (a

PMC/PMD might also activate intercepts under

certain conditions).

Intercept Access Functions—A PCS intercept

is activated when the subject originates a call, receives a call, is provided handover treatment, is

disconnected from a call, uses a vertical service

(e.g., call forwarding, call waiting, three-way calling), registers, or changes his or her service profile

information. The handling of vertical service features is similar to the manner in which those services would be handled through switch-based

solutions and cellular service.

When an intercept is activated, connection is

made to the authorized monitoring site for call

content and control information. Call setup information would be sent to the monitoring site as

it becomes available.

PCS Information Elements

PCS operations use about 70 different message

types to maintain communications and services.

At least 14 of these messages may be of use to law

enforcement agencies. (See table 2-2.)

Location information, when authorized to be

provided to law enforcement officials, is derived

by correlating the Routing Number Bearer Channel and Channel ID to the PCS system component,

e.g., Radio Port (RP), supporting the connection

to the mobile subscriber.

Advanced Intelligent Network (AIN)

AIN architecture distributes the service logic

throughout the network to support the many features and services available to subscribers. Therefore, it may be more difficult to identify calls that

are associated with an intercept subject or to determine the origin or destination of calls to or from

the subject. Additional functions will have to be

built into switch-based solutions to meet the requirements of P.L. 103-414.

AIN is a system of interrelated computer-based

components linked to a switched or wireless telecommunications network that provides a framework for services, e.g., call forwarding, credit card

authentication, personal identification numbers,

speed calling, voice dialing, etc., independent of

the call process. AIN functions reside in network

elements, which can communicate among themselves and with a controlling switch. In some

cases, subscribers can access and control the databases for AIN services (e.g., speed calling lists)

without the intervention of a service provider.
Chapter 2 Technical Aspects of Electronic Surveillance 151

Information Element Description

Radio Personal Terminal Identification

Routing Number

Bearer Channel Identification

Radio Channel Identification

Radio Access System Controller Identification Identifies a specific RASC.

Radio Port Controller Identification Identifies a specific RPC.

Radio Port Identification Identifies a specific Radio Port.

Channel Identification Identifies a specific channel (a timeslot in the signal of a

TDMA [Time Division Multiple Access] system, or one of

several coded signals multiplexed into a CDMA [Code Division Multiple Access] system).

Identifies a specific radio personal terminal or mobile handset (either imbedded in the chipset in the handset, or may

be programmed into a user’s terminal).

A 10-digit geographical telephone number used by the Public Switched Telephone Network to route calls.

A logical name used within the PSC to identify a connection

end-point.

A logical name for the radio path. Timeslots and physical

connections use this name to trace the information flow path

from the radio transceiver to the interface mapping to the

Bearer Channel.

Call Record Information and Charging Information Contains the start and duration of a call. It might also conUniversal Personal Telephone Number

Personal Identification Number

Authentication Key

Access Signaling Information

tain information about the profile of type and frequency of

services used by the subscriber.

Telephone number associated with a user, not a terminal or

a line as in wireline service.

A confidential memorized number used by an individual to

verify their identity to the system.

Information from a magnetically encoded card (substitute for

a Personal Identification Number).

Used to pass supplementary service requests in the signaling channels rather than in the call content channels.

Signal Strength Measurement and Measurement Measure of the amplitude of the signal detected by the RaReference dio Terminal or Radio Port. The reference refers to the decibel measurement used to measure signal strength.
52 | Electronic Surveillance in a Digital Age

AIN19 architecture consists of signaling systems, switches, computer processors, databases,

and transmission media, which provides customized software-controlled services. (See figure

2-8.)

Deployment of AIN is not uniform throughout

the Public Switched Telephone Network (PSTN).

It is being phased into the national system through

progressive upgrades in software modules and intelligent network elements, which increase the

functionality and flexibility of AIN.20 Since AIN

permits peripheral intelligent elements (softwarecontrolled Intelligent Peripherals (IP)) to share

control of a call with switch-software control,

AIN might present special problems to intercepting the communications of wiretap target subjects.21

Signaling System Seven (SS7) switches and

the national network based on the SS7 standard

enable broad deployment of interactive AIN functions in the Public Switched Telephone Network

(PSTN). The SS7 network signaling and processing is carried by an ISDN network. There are three

major groups of technologies in the AIN architecture (See figure 2-8.):

1. Network Elements (NE), Service Switching

Points (SSPs), non-SSP switches, and Signaling Transfer Points (STPs);

2. Network Systems (NS), Service Control Points

(SCPs), Adjuncts and Intelligent Peripherals

(IPS); and

3. Operations Systems (OSs), capabilities that

provide network and service operations as their

primary functions (Operations Systems may be

unique to a service provider).

In general, AIN is not considered to be a part of

the switching system. A switching system may include AIN capabilities, which generally consist of

triggers in call processing and feature software,

that if set, transfers functional control to another

network platform. Many of the intelligent functions are part of the Stored Program Control

Switches (SPCS), thus technical approaches for

meeting law enforcement’s intercept needs at

SPCS are switch-based solutions (supra). However, some of the intelligent peripherals (IP) and

adjunct components contain interactive software

that allows subscribers to directly alter databases

that control services and features available to

them. It may therefore be necessary to query these

peripheral components directly (or via a SPC) to

provide law enforcement agencies the most current information available about an intercept target. This will require special access features that

are not necessarily part of the switching process at

the SPCS.

A Service Switching Point (SSP, See figure 2-8

above.), is a special kind of switch (e.g., an end office switch or a tandem switch) that contains AIN

switch capabilities. A SSP can identify calls

associated with AIN services. When a call is identified that requires AIN treatment, the SSP initiates a dialog with a Service Control Point (SCP) or

peripheral where the information and software

logic for the requested service is located. A nonSSP switch is one that does not have AIN capabili19 AIN architecture has been primarily developed by Bellcore in collaboration with its clients, the Bell Regional Operating Companies

(RBOCs). The interexchange carriers (AT&T, MCI, Sprint, etc.) have similar Intelligent Network (IN) systems in their networks. AIN can also

be deployed in Cellular and Personal Communication Services (PCS).

20 Beginning in 1983, intelligent elements have been progressively introduced into the Public Switched Telephone Network (PSTN). In the

1980s, Phase 1 of Bellcore’s IN architecture (IN/1) was introduced. This was followed by AIN Release 0, AIN 0.1,. . .AIN 0.X. The introduction

of AIN Release 0 in 1991 marked the transition from providing telephone service totally under switch-control software to providing services

through shared control among intelligent network elements.

21 For instance, Service Creation Environments (SCEs) allow nonprogrammer users to create a new service using icons representing functional service blocks without the intervention of the service provider. Service Management Systems (SMSs) allow users direct access to their

services so they can make real-time adjustments as their requirements change.
Chapter 2 Technical Aspects of Electronic Surveillance 153

SOURCE: Electronic Communication Service Providers Committee, 1995

ties, but is able to detect when a call requires AIN complement or compete with the established comprocessing and route them to a SSP for process- munication systems of today. Some of these

ing. technologies have been waiting in the wings for

their time to come as market demand and opportuDeveloping Technologies nities present themselves. Others are of newer vin -

The field of telecommunications is moving rapid- tage, such as some of the developing packet

ly. A stream of new technologies is queued to switching and satellite-based wireless commu-
54 | Electronic Surveillance in a Digital Age

nication systems. The new technologies may—or

likely will—present new obstacles to law enforcement’s needs for electronic surveillance in the

future.

Since the deployment of these new technologies is still in the future, the range and magnitude

of the problems that they may present to law enforcement is a matter of speculation. A couple of

the more prominent technologies that are either in

a preliminary stage of deployment or are poised

for commercial deployment are briefly described

below.

❚ Satellite-Based Wireless Technologies

Satellite technology has been part of the communication system since the middle 1960s. Satellite

communication is an integral part of the international telephone network.22 Today, when highspeed optical fiber capable of carrying immense

volumes of communication to Europe or the Far

East fail, satellite communication links stand

ready to carry the redirected traffic.

Most of the early satellite systems were

matched to the commercial need of wholesale

communications, i.e., from one service carrier’s

switch to another carrier’s switch, hence to wirelines. New satellite systems on the drawing board

or in early phases of implementation will link directly with the user. Some propose to operate

much like cellular or PCS systems, linking the

user and his or her handset directly to the spacebased satellite system.

Two classes of satellite-based communication

services are being considered: GEOS—Geosynchronous Earth Orbiting Satellites; and

LEOS—Low Earth Orbiting Satellites.

Geosynchronous Earth Orbiting Satellites

(GEOS)

GEOS systems will be placed in a geosynchronous orbit at the prescribed distance of 22,300

miles above the equator. These satellite systems

will use a higher transmitting power level than

will the LEOS (because of the difference in distance to the earth). GEOS can be deployed either

in a constellation (several satellites), or as a single

satellite, depending on the nature of the service

that they will deliver.

Deployment of a constellation of GEOS in several different orbit locations can provide global

communication. The system satellites would be

linked by inter-satellite communications to manage the switching and administration. Interconnection with the Public Switched Telephone

Network (PSTN) can be provided, and subscribers

can manage their own communications through

personal ground stations.

A single GEOS satellite can be equipped to aim

spot beams to achieve regional communication

coverage. Such systems operate much like a cellular system (each beam representing a spacedeployed cell site), with switching systems

analogous to the Mobile Cellular Switches

(MCSs) of a ground based cellular system.

The technical impacts of these technologies on

law enforcement agencies’ ability to conduct authorized wiretaps will come from two sources:

1. Caller-to-caller direct links through a satellite

switch that bypasses the terrestrial switched

system; and

2. Jurisdictional problems of conducting authorized wiretaps across the boundaries of sovereign nations.

Low Earth Orbiting Satellites (LEOS)

LEOS are placed in lower orbital positions (500 to

1,400 kilometers [310 to 870 miles]) than are Geosynchronous Earth Orbital Satellites (GEOS).

The lower orbital paths allow them to be operated

with less power and reduce the time delays that

plague communications (time delays limit the

usefulness of GEOS communications for some

time-sensitive applications) using GEOS, which

orbit at distance up to 60 times greater than LEOS.

22 Satellites are used extensively for video, data communication, and for communication with ships at sea. For the purpose of this discussion, the use of satellite based systems for personal wireless applications to the end user will be the focus.
Chapter 2 Technical Aspects of Electronic Surveillance | 55

LEOS systems will be less costly to build and

deploy than GEOS.

There are two classes of LEOS: Little LEOS—

those using many small satellites (36 or more for

global communications); and Big LEOS.23 (See

figure 2-9).

The Federal Communication Commission

(FCC) created the distinction between Big and

Little LEOS based on the allocation of frequencies

to be used (Little LEOS below one Gigahertz; Big

LEOS above one Gigahertz), and services they are

authorized to provide. Little LEOS handle data

traffic only, e.g., messaging, tracking, and monitoring; Big LEOS can provide global mobile telephone service (similar to cellular and PCS) as well

as data services, facsimile, paging, geographic

positioning, and other services tailored to users

needs.

Little LEOS—The services offered by Little

LEOS will primarily operate in nonreal time, i.e.,

store and forward messaging and data. Little

LEOS services are scheduled for deployment and

operation between 1996 and 2000. The service

providers consider emergency and personal communications, law enforcement (vehicle location),

environmental monitoring, utility monitoring

(power grids), shipping cargo management, etc. as

potential markets.

Each Little LEOS system will consist of between 25 and 50 satellites orbiting at about (621

miles) above the earth. One or more earth stations

will serve as a gateway to the space-deployed system. The earth stations may be linked to other peripheral message management nodes, which

could be linked to conventional wireline or wireless communications networks.

Some regulatory matters, domestic and foreign, are yet to be resolved.

Big LEOS—Big LEOS systems are in the development stage, and have not yet been assigned

international frequency allocations, although the

FCC has recently granted licenses to three of the

five potential service providers.

Big LEOS can provide a wide range of voice

and data services, including all of the services provided by Little LEOS, plus cellular- or PCS- like

telephone service. Communications can be from

mobile or fixed Earth stations. These satellitelinked services are considered to be possible alternatives to expensive land-based wire systems in

the remote areas of developing countries. The

cost, however, will be high, and international

country-by-country regulatory questions may

slow global deployment.

Big LEOs, operating at frequencies above one

Gigahertz, will orbit at distances of (310 to 870

miles) above the earth. Communications from a

mobile handset would first seek a transmission

path to a local terrestrial cellular (or PCS) network

(if one exists) for connection to a wireline network. In areas beyond the reach of a cellular network, a direct connection to a satellite station

would be made, which would relay the call back to

earth for connection with a remote wireline network. After cut-through to the wireline network, a

call would be switched as would any other call

originating from a cellular, PCS, or conventional

switched system.

However, Motorola’s proposed Iridium system24 would permit callers to make a direct connection from one handset to another through

23 The terms “big” and “little” have little to do with the physical size of the satellites. The primary difference is the radio frequencies that

have been allocated to each service. “Little” LEOS will operate at frequencies less than one Gigahertz; “Big” LEOS will operate at frequencies

above one Gigahertz. The difference in frequencies affects the nature of the services offered by each of the two LEOS.

24 Motorola’s Iridium system would use 66 LEOS orbiting in 11 different planes of 6 satellites each. This would provide worldwide telephone and data communication linked to 15 to 20 Earth stations connected to terrestrial wireline networks. Satellite-to-satellite cross links

would be capable of data rates up to 25 Million bits/second (Mbps). Several other companies are proposing similar systems, e.g. Globalstar

(Loral and Qualcomm, Inc.), Odyssey (TRW, Inc. and Teleglobe), Ellipso (Mobile Communications Holding, Inc.), ECCO (Equitorial Constellation Communications—Constellation Communications, Inc., Bell Atlantic Enterprises International, and Telecommuniccacoes Brasileiras

S.A.). Not all of these systems will offer intra-satellite communications from caller to caller as will Iridium.
56 I Electronic Surveillance in a Digital Age
Chapter 2 Technical Aspects of Electronic Surveillance | 57

intrasatellite links. Satellite-to-satellite communication could seriously complicate law enforcement’s ability to perform lawful electronic

intercepts.

❚ Packet Switched Transmission

Technologies

The historical evolution of telephone technology

was aimed at optimizing voice communication.

Appeals from the fledgling computer users of the

1960s to the telephone companies for better methods of transmitting data from one computer to

another were largely ignored. This led the government and the computer industry to seek other

means for filling its needs. Thus, two technological cultures developed independently of each other, with little in common between the two and with

little interaction among scientists and engineers in

both camps.25

Today, computers are the telephone network,

and the fastest growing traffic on telephones networks is data and computer-mediated communications. The lingua franca of both telephony

and computer communications is the digital transmission mode. Voice, data, video, and images are

all transmitted, and for practical purposes, look

and are processed the same way. The concept of a

National Information Infrastructure (NII) is based

on the common ground provided by digital

technology that can serve the needs of all users.

While the telephone industry continued to improve the efficiency, quality, and reliability of circuit-connected architecture for voice traffic

(which tends to ebb and flow), the computer communication industry developed packet technologies to handle the bursty (short transactions with

periods of no traffic) nature of high-speed computer data.

A number of packet-switched networks were

deployed to meet the increasing need for computer

communication. Many of these networks were

part of a national computer network inspired by

the Department of Defense (DOD) in the late

1960s to meet its mission needs.26 DOD was

instrumental in developing packet network

technology and packet protocols (the rules for formatting, addressing, and routing the packets within the network). The DOD protocols and routing

technology (Transmission Control Protocol/Internet Protocol—TCP/IP) has become a defacto industry standard, and the operating standard for the

Internet. The Internet’s phenomenal growth and

success spawned the vision of a National Information Infrastructure (NII), which appears poised to

subsume all telecommunications under its aegis.

Prior to the development and deployment of

packet-switched networks, computer users relied

on modems (modulate/demodulate) for communication over the telephone network. Modems

convert the digital signals produced by a computer

to electrical signals (analog signals) that look and

behave in the telephone network as though they

were sounds or spoken words. At the receiving

modem, the analog electrical signals are converted back to digital form before re-entering the

receiving computer. Modem technology is still a

common means for communicating between

computers over the Public Switched Telephone

Network (PSTN). However, the speed of modem

transmission is relatively slow and thus limits

their usefulness for high-speed, broadband applications, e.g., video and images.

A packet-switched network can send information over several different routes (like choosing alternative interconnected highways) to reach a

destination. Data placed in packets (segments of

25 Even today the schism between the two industries remains evident. The two cultures continue to exist, with different language and different perspectives on communications, although both use common digital technology and are being forced to act as one, if ever so reluctantly.

26 A number of regional networks and Internet service providers have appeared to meet the increasing demand. Many of these entities lease

lines from the Public Switched Telephone Network (PSTN), although the Internet operates independently of the PSTN.
58 | Electronic Surveillance in a Digital Age

data and routing information) containing special

control information (source and destination address) are sent along any route within the network

that happens to be available that leads to the addressee.27 Because of the random nature of the

route to the destination taken by packets, they arrive at different times and out of order, although

each contains only a portion of the data or message

sent by the originating computer. Packets must be

assembled and disassembled at the receiving end

and put in the same order or sequence as they were

sent.

Intervening years have brought increased demand for switched broadband networks to handle

the high capacities needed for video, images, and

data. In response to this the telephone industry has

attempted to recoup the business it lost to private

networks and information service providers by

improving its computer communication services.

In 1976, the telephone industry adopted an international packet switching standard designated

X.25, a relatively slow transmission service.28

Since then, Switched Multimegabit Data Service

(SMDS) and Frame Relay (a technology that uses

packets of variable payload length)29 have been

introduced. Both SMDS and Frame Relay are precursors of what the telephone industry considers

to be its technology backbone of the future—the

Asynchronous Transfer Mode (ATM)

Asynchronous Transfer Mode (ATM)

ATM is a fast packet switching technology, i.e., it

provides fast processing power that can keep up

with the increased bandwidth (volume) available

with very fast transmission systems over optical

fiber, which are required for video. ATM is flexible enough to support voice, video, images, and

data. It is a scaleable technology, i.e., it can be

used to link a few computers in an office setting, it

can serve a campus setting, like Capitol Hill, it can

be expanded to cover an area the size of Washington, DC., or it can work in a national network, as

proposed for the National Information Infrastructure. It has the added advantage of being accepted

and supported by both the computer industry and

the telecommunications industry.

ATM has two distinguishing features:

1. It is cell-based. Instead of variable-length

frames, as used by Frame Relay and other

packet networks (sometimes several thousand

bytes, which contain 8 bits of binary information), ATM uses fixed-length cells. (See figure

2-10.)

2. ATM is connection-oriented, i.e., every cell in

the ATM transmission travels over the same

route. The network path, or virtual circuit, is

designated during call setup by information

contained in the cell header. The header in the

ATM cell contains the information a network

needs to relay the cell from one network node

(switching point) to the next over the pre-established route.

ATM connections are sets of routing tables retained in an ATM switch, which are matched with

the address contained in an ATM cell header. ATM

addresses, unlike a geographically locatable Directory Number (DN) or a TCP/IP packet, only

have meaning for locating one point (node) in an

ATM net to the next node.

Each ATM switch is provided with a set of

lookup tables (computer database), which identify

an incoming cell by header address, route it

through the switch to the proper output port, and

overwrite the incoming address with a new one

that the next switch along the route will match

with an entry in its routing table. Thus, the message is passed along from switch to switch, over a

prescribed route, but the route is virtual, since the

switch carrying the message is dedicated to it only

while the cell is passing through it. 

27 Packets have been compared to envelopes used for traditional mail. The data or information in the packet data field is like the writing on

paper, and the numerical address of the computer to which it is sent that is contained in the packet header is like the address on an envelope.

28 X.25 packet switching carries a relatively low data rate of approximately 9.6 kilobits/second.

29 Frame Relay is not based on fixed-length data frames, it uses flags in the header and trailer to indicate the beginning and end of frames.
I

Chapter 2 Technical Aspects of Electronic Surveillance 159

I VPI I Vcl I

Vcl

GFC =generic flow control

VPI = virtual path identifier

VCI = virtual channel identifier

PT = playbill type

CLP = cell loss priority

HEC = header error control

Frame relay packet

Key’ GFC=generic flow control, VPl=vlrtual path identifier, VCl=virtual channel identifier; PT=playbill type, CLP=cell

loss priorly, HEC=header error control

SOURCE James Lane, IEEE Spectrum, p 43, February 1994

The address in the header of an ATM cell contains two fields:

1. Virtual Path Identifier (VPI); and

2. Virtual Channel Identifier (VCI).

The two-part addressing scheme allows the network to designate major trunks between locations,

and identify the individual circuits (channels)

within the trunk. A virtual path may consist of

several virtual channels. Thus, the VPI might represent a trunk between two cities. The VCIs might

represent individual calls. Switching equipment

along the network can route all the calls on the basis of just the VPI without having to query the rest

of the address (VCI) until the trunk gets to the final

location, where the individual calls are distributed

to their destinations. (See figure 2-11.)

Implications for Electronic Surveillance—If

ATM becomes the enabling technology for the nation’s next generation of multimedia networks

(the NII) as some foresee, interception of electronic communication will become more difficult.

Packet networks will require a substantially dif-
60 I Electronic Surveillance in a Digital Age

SOURCE Off Ice of Technology Assessment, 1995

ferent approach to surveillance than used for

today’s digital telephony. Since the address is an

integral part of the packet that contains the message data as well, it will be necessary to develop

means to insert hooks into the packet header to

identify the sender and the intended recipient.

Packets in connectionless services, e.g., Internet (TCP/IP), and Frame Relay, have destination

addresses embedded in the packet that are identifiable with a physical location and/or an individual.

A packet may travel any number of alternate

routes in reaching its destination. Since information is segmented into variable length packets,

connectionless routing can result in a packet containing part of the message that is sent before

another, may reach its destination after the second

or later packets that are sent. Connectionless packets must be reassembled in proper order to make

sense of the message. Once a message is sent by an

intercept subject, random routing will complicate

the process of identifying the packets—and only

the packets—that are authorized to be lawfully intercepted until they reach their destination.

ATM establishes a virtual circuit between ATM

switches (but not physical connections as used in

the Public Switched Telephone Network) that

routes each ATM cell over the same trunk and

channel. Many different calls (video, voice,

images, data) in addition to that of the intercept

subject or his or her correspondent maybe moving

over the same routes simultaneously and/or intermittently. The route in the header address is overwritten with a new address at each ATM switch,

which is translated from the switch route lookup

table. The unique routing protocol of ATM will require new approaches to message identification

and verifications and will complicate trap and

trace and pen register procedures.

Internet (TCP/IP) and Frame Relay packets can

be sent over ATM networks, although ATM cannot recognize the embedded packet addresses in

the headers. ATM incorporates the entire TCP/IP

or Frame Relay packet into an ATM cell and readdresses the cell according to the ATM routing protocol. At the point of termination, the ATM

envelope is stripped away and the TCP/IP packets

are assembled for processing by the recipient.

This may further complicate the identification and

association of a call from or to the subject of a lawful electronic intercept. Moreover, there is currently a market in redirecting TCP/IP traffic, or

changing a sender’s address to an anonymous ad-
Chapter 2 Technical Aspects of Electronic Surveillance | 61

dress. Some of these services are based in foreign

jurisdictions, thus possibly complicating the legal

procedure for identifying communications from

or destined for a lawful intercept subject.

In addition to the technical difficulty in dealing

with packet-based communication in general, and

ATM networks in particular, the legal requirements for establishing a lawful electronic intercept may be more difficult. The isolation of an

intercept subject’s outgoing and incoming traffic

according to the strict requirements that assure the

privacy of other communicants may be more difficult. Minimization, i.e., screening or filtering

nongermane information from the intercepted

communication, also may be more complicated.
Appendix B:

 Electronic Surveillance

Requirements Keyed

 to P.L. 103-414

REQUIREMENT 1

A) Law enforcement agencies require access to

the electronic communications transmitted,

or caused to be transmitted, to and from the

number, terminal equipment, or other identifier associated with the intercept subject

throughout the service areas operated by the

service provider served with a lawful authorization. Law enforcement agencies also require access to generated call-identifying

information necessary to determine the calling and called parties. Law enforcement agencies will coordinate delivery of these

communications with the service provider in

accordance with Requirement 3(A) infra for

each service area. (Sec. 103(a)(1), Sec.

103(a)(2))

B) Law enforcement agencies require real-time,

full-time monitoring capability for interceptions. (Sec. 103(a)(1))

C) Law enforcement agencies require telecommunications carriers to make provisions for

implementing a number of simultaneous interceptions. (Sec. 103(a)(1))

D) Law enforcement agencies require telecommunications carriers to expeditiously provide

access to the communications of the intercept

subject. (Sec. 103(a)(1))

REQUIREMENT 2

Law enforcement agencies require:

1) information from the telecommunications carrier to verify the association of the intercepted

communications with the intercept subject,

and

2) information on the services and features subscribed to by the intercept subject prior to and

during the intercept implementation. (Sec.

103(a)(2))

REQUIREMENT 3

A) Law enforcement agencies require telecommunications carriers to transmit intercepted

communications to a monitoring facility designated by the law enforcement agency. (Sec.

103(a)(3))

B) During the intercept period, law enforcement

agencies require that the reliability of the services supporting the interception at least

equals the reliability of the communications

services provided to the intercept subject.

(Sec. 103(a)(3))

C) Law enforcement agencies require that the

quality of service of the intercepted transmissions forwarded to the monitoring facility

| 67
68 | Electronic Surveillance in a Digital Age

comply with the performance standards of the

telecommunications carriers. (Sec. 103(a)(3)

REQUIREMENT 4

Law enforcement agencies require the intercept to

be transparent to all parties except the investigative agency or agencies requesting the intercept

and specific individuals involved in implementing the intercept capability. Law enforcement

agencies require the implementation of safeguards to restrict access to intercept information.

(Sec. 103(a)(4))
Appendix C:

Related

 OTA Reports for

Further Reading

 U.S. Congress, Office of Technology Assessment, Critical Connections: Communication for the Future, OTA-CIT-408 (Washington, DC: U.S. Government Printing Office, January 1990)

 U.S. Congress, Office of Technology Assessment, The 1992 World Administrative Radio Conference:

Technology and Public Policy, OTA-TCT-549 (Washington, DC: U.S. Government Printing Office,

May 1993)

 U.S. Congress, Office of Technology Assessment, Advanced Network Technology, OTA-BPTCT-101 (Washington, DC: U.S. Government Printing Office, June 1993)

 U.S. Congress, Office of Technology Assessment, Protecting Privacy in Computerized Medical Information, OTA-TCT-576 (Washington, DC: U.S. Government Printing Office, September 1993)

 U.S. Congress, Office of Technology Assessment, Information Security and Privacy in Network Environments, OTA-TCT-606 (Washington, DC: U.S. Government Printing Office, September 1994)

 U.S. Congress, Office of Technology Assessment, Wireless Technology and the National Information

Infrastructure, (to be released Summer 1995)

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lossary

Access

The technical capability to interface with a communications facility, such as a communications

line or switch, so that law enforcement can monitor and receive call setup information and call

content.

Actual Capacity

That portion of the Maximum Capacity simultaneously required to conduct electronic surveillances at or before a specified date in a given

switch as indicated by the Attorney General for all

government agencies authorized to do surveillance.

Advanced Intelligent Network (AIN)

A system of interrelated computer-based components linked to a switched or wireless telecommunications network that provides a framework for

services, e.g., call forwarding, credit card authentication, personal identification numbers, speed

dialing, voice dialing, etc.

Base Station

The common name for all of the radio equipment

located at a single site for serving one or several

cells.

Call

Any wire or electronic signaling information generated by a human or a computer acting as an agent

for a human to set up a physical or virtual connection to transit information to another or multiple

users (humans and/or computer processes).

Call Content

The same as “contents” as defined in 18 U.S.C.

2510 (8) and with respect to any electronic communication, includes any information concerning

the substance, purport, or meaning of that communication.

Call Content Channel (CCC)

The link between the surveillance switch and the

law enforcement agency that carries the call content. The CCC may be a switched connection or a

dedicated path through the Public Switched Telephone Network (PSTN), e.g., on a private line.

Call Data Channel (CDC)

The interface between the surveillance switch and

the law enforcement agency that carries the call

set-up data. The CDC may be a switched connection or dedicated path through the Public

Switched Telephone Network (PSTN) or may be

separate from the PSTN, e.g., via a private line or a

packet switched network.

Call Setup Data

Includes all of the setup and call release information received and interpreted by the surveillance

switch as a regular part of processing the call as

defined in applicable standards and specifications

for the services being provided. For example, this

includes the initial digits dialed to access an Interexchange Carrier (IC) but may not include those

dialed via Dual Tone Multi-Frequency (DTMF)

after connection with the IC.

Call Setup Information

When used with respect to any electronic communication, the information generated during the establishment of communications or transmission

of a protocol data unit such as a datagram, that

identifies the origin and destination of the call. For

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72 | Electronic Surveillance in a Digital Age

voice communications, this information is typically the electronic pulses, audio tones, or signaling messages that identify the numbers dialed or

otherwise transmitted, or caused to be transmitted, by the intercept subject. It also includes incoming pulses, tones, or messages that identify

the number of the originating instrument, device,

or user. For data services, this information is typically the source (calling) address and destination

(called) address contained in fields of the data

unit, such as in the header of a frame or packet.

Calling Features Indicator

The authorization and activity status of the Mobile

Switch features, including call forwarding (unconditional, busy, no answer), call waiting, threeway calling, and call delivery.

CDMA

Code-Division Multiple Access.

Central Office

In telephone operations, the facility housing the

switching system and related equipment that provides telephone services for customers in the immediate geographical area.

DTMF

Dual tone, multi-frequency, i.e., push button dialing.

Electronic Communications

The same as defined in 18 U.S.C. 2510 (12), any

transfer of signs, signals, writing, images, sounds,

data, or intelligence of any nature transmitted in

whole or in part by a wire, radio, electromagnetic

photo-electric, or photo-optical system, etc. The

term includes “wireless communication,” as defined in 18 U.S.C 2510 (1).

Electronic Serial Number

A coded serial number assigned by the manufacturer to the mobile unit.

Electronic Surveillance

The statutory-based process and the associated

technical capability and activities of law enforcement agencies related to the interception and monitoring of electronic communications.

Handoff

Occurs when a subscriber travels from one service

area to another while a wireless call is in progress.

Home Location Register (HLR)

The location register to which a user identity is assigned for record purposes, such as subscriber information (e.g., Electronic Serial Number,

Directory Number, Profile Information, Current

Location, Validation Period). The HLR may or

may not be located within, and be indistinguishable from, a Mobile Switching Center (MSC). A

HLR may serve more than one MSC and the HLR

may be distributed over more than one physical

entity.

Home Service Area

The service area in which a customer has subscribed to receive service.

Intercept Subject

Person or persons identified in the lawful authorization and whose incoming and outgoing communications are to be intercepted and monitored.

Interface

A shared boundary or point common to two or

more similar or dissimilar command and control

systems, subsystems, or other entities against

which, or at which, or across which useful information takes place.

Local Exchange

An exchange where subscribers’ lines are terminated.

Local Switch

A switch that connects one customer’s line to

another customer’s line, or to a facility that goes to

another switching system, i.e., a trunk.

Maximum Capacity

That switch capacity (in terms of the number of simultaneous surveillances and the number of simultaneous monitorings) that cannot be exceeded

in a switch without revision of its generic software.
Glossary | 73

Mobile Identification Number

An identification number assigned by the service

provider to a subscriber.

Mobile Station (MS)

The interface equipment used to terminate the radio path at the user. It provides the user the ability

to access network services.

Mobile Switching Center (MSC)

An automatic switching system that constitutes

the interface for user traffic between the cellular

network and public switched networks or other

MSCs in the same or different cellular networks.

Monitoring

The process of capturing information, either call

content or call set-up information or both, in real

time during he processing of a call. (This does not

include nonreal time access to stored data such as

billing records for previous calls or subscription

parameters).

Multiple Agency Distribution

The capability to provide multiple surveillances

of a given access to a target to satisfy the needs of

more than one government agency by some appropriate means.

Multiplex (MUX)

Use of a common channel to make two or more

channels. This is done either by splitting of the

common channel frequency band into narrower

bands, each of which is used to constitute a distinct channel (frequency division multiplex), or

by allotting this common channel to multiple users in turn, to constitute different intermittent

channels (time division multiplex).

Packet Switching

A system whereby messages are broken down into

smaller units called packets that are then individually addressed and routed through the network.

Pen Register

A device that records or decodes electronic or other impulses that identify the numbers dialed or

otherwise transmitted on the telephone line to

which such device is attached. Pen Register is an

archaic name that survived the transition from

pulse dialing to touch-tone dialing. The recording

device is now called a “Dial Number Recorder”

(DNR). The term does not include a device used

by a service provider for billing, or recording incidental to billing, for communications services, or

any device used by a service provider for cost accounting in the course of business.

Private Branch Exchange (PBX)

Small local telephone office, either automatic or

manually operated, serving extensions in a business complex and providing access to the public

switched telephone network.

Remote Switch

A switch associated with, and controlled by, an

exchange in a different location (host switch).

Host switches can serve several remote switches,

and are connected to the remotes with facility

links.

Roaming

When the subscriber initiates or receives a call in

other than his or her home service area.

Service Profile Information

The set of features, capabilities, and/or operating

restrictions associated with a subscriber, e.g., account code digits, alternate billing digits, etc.

Service Switching Point (SSP)

A specially designed switch that contains Advanced Intelligent Network (AIN) switching capabilities.

Stored Program Control Point (SPCP)

A computer component that stores many of the intelligent functions of an Advanced Intelligent

Network (AIN).

Surveillance

The process of maintaining watch on a target, on

behalf of a single law enforcement agency, for the

occurrence of originating or terminating calls that

must be monitored or for any other activity that

must be recorded, such as administrative changes

to the service parameters.

Surveillance Switch

The circuit switch which identifies calls made

from or to the target and which performs surveillance. This is normally the local exchange (or endoffice) serving that target.
74 | Electronic Surveillance in a Digital Age

Tandem Switch

A switch that connects trunks to trunks.

Target

An identifiable origination or termination of a

telecommunications call. The most common

identifier is the telephone number (or “DN”) that a

call is made to or from, but other identifiers may

also be used.

TDMA

Time Division Multiple Access

Transmission

The act of transferring a sign, signal, writing,

image, message, sound, data, or other form of intelligence (information) from one location to

another by a wire, radio, electromagnetic, photoelectronic, or photo-optical system.

Transparency

The circumstances wherein the parties to a communication and unauthorized individuals (i.e., individuals who are not involved in implementing

and maintaining the intercept) are unaware of ongoing electronic surveillance.

Trap and Trace Device

A device that captures the incoming electronic impulses that identify the originating number of an

instrument or terminal from which electronic

communication is transmitted.

Trunk

A circuit between two ranks of switching equipment in the same office, or between different

switching centers or different central offices.

Verification

The process whereby law enforcement can adequately demonstrate to a judge or jury that the

number or other identifier (e.g., telephone number, electronic mail address) targeted for interception corresponds to the person or persons whose

communications are being intercepted.

Visitor Location Register (VLR)

The location register other than the Home Location Register (HLR) used by a Mobile Switching

Center (MSC) to retrieve information for handling

of calls to or from a visiting subscriber. The VLR

may or may not be located within, and be indistinguishable from, an MSC. The VLR may serve

more than one MSC.