N4T L INST OF STAND & TECH R.LC

A111Q3 SEQ7EM

NIST

PUBLICATIONS

NIST Special Publication 800-13

U.S. DEPARTMENT OF

COMMERCE

Technology Administration

National Institute of Standards

and Technology

Telecommunications Security

Guidelines for Telecommunications

Management Network

John Kimmins, Charles Dinkel, and Dale Walters

COMPUTER SECURITY

NO

Nisr . 800-1 3

1995
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'At Boulder, CO 80303. ^Some elements at Boulder, CO 80303.
NisT Special Publication 800-13 TelecomiTiunications Sccurity

Guidelines for Telecommunications

Management Network

Jdin Kimmins,* Charles Dinkel, and Dale Walters

* Bellcore

COMPUTER SECURITY

Computer Systems Laboratory

National Institute of Standards

and Technology

Gaithersburg, MD 20899t0001

October 1995

OF

U.S. Department of Commerce

Ronald H. Brown, Secretary

Technology Administration

Mary L. Good, Under Secretary for Technology

National Institute of Standards and Technology

Arati Prabhakar, Director
Reports on Computer Systems Technology

The National Institute of Standards and Technology (NIST) has a unique responsibility for computer

systems technology within the Federal government. NIST's Computer Systems Laboratory (CSL) develops standards and guidelines, provides technical assistance, and conducts research for computers and

related telecommunications systems to achieve more effective utilization of Federal information technology resources. CSL's responsibilities include development of technical, management, physical, and administrative standards and guidelines for the cost-effective security and privacy of sensitive unclassified

information processed in Federal computers. CSL assists agencies in developing security plans and in improving computer security awareness training. This Special Publication 800 series reports CSL re- search and guidelines to Federal agencies as well as to organizations in industry, government, and

academia.

National Institute of Standards and Technology Special Publication 800-13

Natl. Inst. Stand. Technol. Spec. Publ. 800-13, 44 pages (Oct. 1995)

CODEN: NSPUE2

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1995

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402
Abstract

The Public Switched Network (PSN) provides critical commercial telecommunications services and

National Security and Emergency Preparedness (NSEP). Telecommunication Service providers, equipment

manufacturers, users, and the Federal Government are concerned that vuhierabilities in the PSN could be

exploited and result in disruptions or degradation of service. To address these threats, the National Institute

of Standards and Technology (NIST) is collaborating with Bellcore to investigate the vulnerabilities and

related security issues that result from the use of open systems architectures in the telecommunications

industry. Security features required to counter the threats are identified.

This guideline focuses on two specific components of a Telecommunications Management Network (TMN)

- Network Elements (NEs) and Mediation Devices (MDs) - with emphasis on the security features needed to protect the Operations, Administration, Maintenance, and Provisioning (OAM&P) of these components.

This document is intended to provide a security baseline for NEs and MDs that is based on commercial

security needs. In addition, some National Security and Emergency Preparedness (NS/EP) security

requirements will be integrated into the baseline to address specific network security needs.

The guideline should assist telecommunications vendors in developing systems and service providers in

implementing systems with appropriate security for integration into the PSN. It can also be used by a government agency or a commercial organization to formulate a specific security policy. It does not

stipulate regulatory requirements or mandated standards of the National Institute of Standards and

Technology.

iii

TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

1.0 PREFACE 1 1.1 INTRODUCTION 1 1.1.1 BACKGROUND 1 1.1.2 SCOPE OF TSG EFFORT 2

1.1.3 DEFINITIONS 5 1.1.4 AUDIENCE 6

1.1.5 TERMINOLOGY 7

1.1.6 CONFORMANCE 7

1.1.7 APPLYING THE TSG 8

1.1.8 AREA FOR FURTHER RESEARCH 8

2.0 SECURITY THREATS AND CONCERNS 9

2.1 INTRODUCTION 9

2.2 SCOPE OF SECURITY THREATS 9

2.3 SOURCES OF THREATS 10

2.3.1 EMPLOYEES/INSIDERS 10

2.3.2 NATURAL DISASTERS 10

2.3.3 MALICIOUS HACKERS 10

2.4 THREAT CATEGORIES 11

3.0 REQUIREMENTS FRAMEWORK 12

3.1 REQUIREMENTS APPLICABILITY 12

3.1.1 MEDL\TION DEVICES AND ELEMENT MANAGERS 12

3.1.2 COMPONENT VIEW 12

3.1.3 SECURITY POLICY 12

3.1.4 USER ACCESS 12

3.1.5 FRAUD 13

3.1.6 NEW TECHNOLOGIES 13

3.2 HIGH LEVEL SECURITY REQUIREMENTS 13

4.0 DETAILED GUIDELINE 15

4.1 IDENTIFICATION 15

4.2 AUTHENTICATION 15

4.3 SYSTEM ACCESS CONTROL 18

4.4 RESOURCE ACCESS CONTROL 19

4.5 DATA AND SYSTEM INTEGRITY 19

4.6 AUDIT 20

4.7 SECURITY ADMINISTRATION 21

4.8 DATA CONFIDENTIALITY 23

5.0 DEVELOPMENT LIFE CYCLE REQUIREMENTS 24

5.1 SECURITY POLICY 24

5.2 REQUIREMENTS ANALYSIS 24

5.3 SYSTEM DESIGN 24

5.4 DETAILED SYSTEM DESIGN 25

5.5 IMPLEMENTATION 25

5.6 DEVELOPMENT ENVIRONMENT 25

5.7 SYSTEM TEST 26

5.8 PACKAGING AND DELIVERY 26

V
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

5.9 DOCUMENTATION 27

5.10 SUPPORT 28

LIST OF ACRONYMS 29

REFERENCES 30

APPENDIX 32

vi
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

1.0 PREFACE

The Public Switched Network (PSN) provides critical commercial telecommunications services and National Security and

Emergency Preparedness (NS/EP)' telecommunications. Service providers, equipment manufacturers, users, and the Federal

Government are concerned that vulnerabilities in the PSN could be exploited and resuh in disruptions or degradation of

service. To address these threats, the National Institute of Standards and Technology (NIST) is collaborating with Bellcore

to investigate the vuhierabilities and related security issues that result from the use of open systems architectures in the

teleconmiunications industry. Security features required to counter the threats are identified.

A series of Telecommunication Security Guidelines (TSGs) that address a hierarchy of telecommunication architectures

of increasing complexity may be produced. This first guideline focuses on two specific components of a Telecommunications Management Network (TMN)^ - Network Elements (NEs) and Mediation Devices (MDs) - with

emphasis on the security features needed to protect the Operations, Administration, Maintenance, and Provisioning

(OAM&P) of these components.

This TSG is intended to provide a security baseline for NEs and MDs that is based on commercial security needs. In

addition, some NS/EP security requirements will be integrated into the baseline to address specific network security needs.

The guideline should assist telecommunications vendors in developing systems and service providers in implementing

systems with appropriate security for integration into the PSN. It can also be used by a government agency or a commercial

organization to formulate a specific security policy. It does not stipulate regulatory requirements or mandated standards

of the National Institute of Standards and Technology.

1.1 INTRODUCTION

1.1.1 BACKGROUND

The Public Switched Network (PSN) provides services that are essential to U.S. citizens and government agencies alike.

Disruption of telecommunications services would clearly represent a serious threat to public safety and security. A 1989

report of the National Research Council, "The Growing Vulnerability of the Public Switched Network," [1] outlined the concerns ofthe government for maintaining the integrity of the PSN against intruders. A report the following year by the

President's National Security Telecommunications Advisory Committee (NSTAC) concluded that "until there is confidence

that strong, comprehensive security programs are in place, the industry should assume that a motivated and resourceful

adversary, in one concerted manipulation of the network software, could degrade at least portions of the PSN and monitor

or disrupt the telecommunications serving [government] users" [2]. In addition, outages experienced by service providers

in the recent past have focused the Federal Government's attention on the need to ensure that telecommunications services

are available and rehable. More recent NSTAC studies have shown that the threat and vulnerabilities for public networks

is still significant [18].

In the past, there were relatively few telecommunications providers, and the systems they used were built on proprietary

"NS/EP telecommunications services are telecommunications services which are used to maintain a state of readiness or to respond to and

manage any event or crisis (local, national, international) which causes or could cause injury or harm to the population, damage to or loss of

property or degrades or threatens the NS/EP posture of the United States" [19]

2See the Appendix for a description of a TMN architecture

1
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

platforms. The Federal Communication Commission's (FCC) Open Network Architecture (ONA) requirements specify

unbundled and equal access to the PSN for Bell Operating Companies and their enhanced services competitors [3]. The

environment is changing today to one where many service providers are using products and offering services that must work

with products from many vendors [4], [5], [6]. This new open telecommunications enviroimient has been characterized as one with: a large number of features; multi-media, multi-user services; incomplete knowledge of the feature set by service

designers; lower skill and knowledge levels of some service creators; multiple execution environments from different

vendors; and distributed intelligence [7]. A Network Operations Forum (NOF) report notes that:

While the advent of open systems interfaces has assisted the acceptance and international deployment of

networking technology, it has also seen a downside in that it has become easier to intrude on networks designed

with such open features. ... Bellcore's security Subject Matter Experts have indicated that many of the intruders were assisted in their endeavors by the opeimess and standardization that the telecommunications industry has

undergone during the last decade [8].

Fraudulent use of telecommunications resources is also on the increase. Intruders are taking advantage of different

situations to commit fraud. Two situations are listed below:

1 . Customers frequently fail to adequately protect their customer premises equipment (CPE) which allows

intruders to steal service without modifying data, information, or software confrolling Network Elements

(NEs).

2. Customers have demanded and received greater access to data, information, and software controlling

NEs to expand their capabilities to confrol and customize their service. Intruders gain unauthorized

access to customers' capabilities and steal service by modifying data, information, or software

controlling NEs.

The second situation is of greater concem, because in addition to simple theft of service, it creates the potential for intruders

to cause denial of service that may affect a large number of users.

Safeguarding the security and integrity of the PSN in such an environment is a challenging task. In the current open

environment, industry/government cooperation will help ensure that organizations implement the baseline security measures needed to protect their systems. This document provides baseline protection measures that govenmient agencies or commercial organizations can use to safeguard Telecommunication Management Networks (TMN) resources and counter

security threats.

1.1.2 SCOPE OF TSG EFFORT

Telecommunications networks offer a wide range of communication services (packet switching, data fransfer, voice, video,

etc.) to customers. These networks, which may be public or private, are populated by a large and increasing number of

Operations Systems (OSs), Network Elements (NEs), Element Managers (EMs) and Mediation Devices (MDs) supplied

by different vendors.

OSs tend to have cenfralized functionality, a span of control that covers a large portion of the network, and generally

provide most of the operations functions. NEs are distributed components that provide telecommunications services, have

a span of control generally limited to themselves, and have a relatively limited set of operations functionality. MDs act on the context of operations information passing between NEs and OSs. MDs may provide functions such as upper layer

protocol intemetworking, filtering, format conversion, storage, etc. The Appendix provides more detail on the differences

among these components.

2
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

A TMN allows for the exchange of management information and offers communications between itself and the

telecommunications networks. Management information about most aspects of network operations, including testing,

maintenance, billing, and engineering is exchanged over TMN interfaces. TMNs provide the organized network structure

that is needed to interconnect various types of OSs and telecommunications equipment using standardized protocols and

interfaces.

The rapid growth in the number of telecommunications networks and the variety of services they offer have created a wide

diversity of management and security needs to be satisfied. TMN interfaces, such as those between NEs and OSs, are vulnerable to a variety of threats. Adequate security measures must be provided to protect them. The connectivity provided

by open systems accentuates the security risks of unauthorized access to the TMN environment and its software and

databases.

The Telecommunication Security Guidelines ( TSG) for TMN will define a fi-amework and provide guidance for

estabUshing a secure TMN. Security in a TMN refers to a set of procedural, logical, and physical measures that prevent,

detect and correct certain types of actions or threats that may compromise the integrity, availability, timeliness, and

confidentiality of information and services. Security mechanisms for the interfaces and communications required to manage the various Operations, Administration, Maintenance, and Provisioning (OAM&P) functions in a TMN are discussed.

Various levels of decomposition exist within a telecommunications network. The TMN architecture provides one such level. The first phase of this effort will address the network at a component level. Subsequent phases will address both

component and global levels.

1.1.2.1 SCOPE OF SECURITY FEATURES

This first of a series of TSGs describes security features that are necessary to protect TMN components, specifically NEs

and MDs, firom various types of attacks leading to misuse and abuse of the software fixnctions within the components.

These security features address such areas as authentication, access control, audit, integrity, and administration. This

document addresses both the global nature of the TMN and the interactions among TMN components.

Security features are not sufficient by themselves to provide a secure TMN. Security has to be considered throughout the

entire development life cycle of the TMN and its components as part of quality assurance and system reliability. All

security features need to be properly conceived, designed, implemented, tested, installed, documented, and maintained.

Otherwise, a false sense of security may result. This TSG effort specifies appropriate security requirements to ensure that an acceptable security level is maintained throughout the system development life cycle and is also reflected in system

documentation.

1.1.2.2 PERSPECTIVES

1.1.2.2.1 TELECOMMUNICATIONS SECURITY GUIDELINE

This Telecommunications Security Guideline adopts an OAM&P perspective rather than a user service perspective. This

document describes security features needed by the networic nodes and the network to protect themselves fi"om various types

of security threats and attacks. The focus is on the security of NE and MD operations, NE/MD interactions with other

components, information resident in the NE, and firaud prevention.

The security features will not address security in the context of the inherent features in the network's call processing

fimctions or how various network services will provide security within the firework of the service. The OAM&P of the

3
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

infomiation and software used by the network to process a call or a service request are within the purview of this effort.

Emphasis is placed on defining a minimum security baseline to protect the TMN components fi-om various security threats.

It is recognized that network environments and service needs will vary. This document will establish a security baseline

that is apphcable to a common commercial level of security. For some user enviroimients, additional security features and

stronger mechanisms may be needed to augment the specified baseline, depending on the organizational security policies.

1.1.2.2.2 MINIMUM SECURITY REQUIREMENTS/COMMON CRITERIA

NISTIR 5153, Minimum Security Requirements for Multi-User Operating Systems (MSR), specifies computer-based

protection mechanisms for the design, use, and management of information systems. These requirements include technical measures that can be incorporated into multi-user, remote access, resource sharing, and information-sharing computer

systems. The MSR provides administrators of an MSR-conformant computer system with the tools to control the sharing

of information and resources based primarily on the identity of users, but also on the time of day, terminal location, or type

of access requested by users. The technical measures also provide tools to protect against common user actions that may

compromise security and against deliberate penetration attempts by "crackers^". In addition, there are requirements that a conformant computer system provide a tailorable ability to log events that may impact the security of either the system

or the information that it is processing.

The MSR provides basic commercial computer system security requirements applicable to both govenmient and

commercial organizations. The MSR document was written fi-om the perspective of protecting the confidentiality and

integrity of an organization's resources and promoting the continual availability of these resources. The MSR is being

superseded by the draft Common Criteria."*

1.1.2.2.3 DIFFERENCES BETWEEN THE TSG AND MSR

In the past, differences between telecommunications systems and computer systems were readily apparent. Today that

distinction is not so clear. For example, one type of NE, the software-controlled digital switch, has replaced much of the

older mechanically switched telecommunications equipment. The newer digital systems are taking on the characteristics

of special purpose computer systems processing a communication application. As such, they are subjected to many of the same threats that confront computer systems, while at the same time retaining much of the unique functionality associated

with responding to customer demands for voice communications.

The TSG and the MSR/Common Criteria take different approaches to dealing with security. The latter can be used to specify a set of security requirements needed in a class of computer products often described as general purpose, multi-user

operating systems. The Common Criteria is intended to broaden its scope to include requirements for trusted subsystems

and distributed systems. Examples of such products from the TMN environment (architecture) include Operations Systems

(OSs) and Workstations (WSs). The MSR is based on the TCSEC' C2 criteria class, with additions from current computer

A cracker is a computer hacker who specializes in overcoming software protection systems.

4The Common Criteria will allow for the creation of protection profiles for general purpose, multi-user operating systems, trusted components, and secure distributed systems. It is anticipated that these profiles, or a version thereof, will form the basis for mutual recognition of

system evaluations among nations.

^The Department of Defense Trusted Computer System Evaluation Criteria (TCSEC) describes criteria for specifying and evaluating the trust

of operating systems. It is widely known as the "Orange Book."

4
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

industry practice and commercial security requirements specifications.

In contrast, the focus ofthe TSG is on NEs and MDs - con^nents that differ from the general purpose computers normally

associated with OSs and WSs. Also, the fiiU functionality of an NE can include call-handling OAM&P fixnctions as well

as a billing capability.

Security requirements for TMN components such as OSs and WSs are addressed by the MSR/Common Criteria. For that reason the TSG does not deal with such systems, but instead focuses on the remaining components of the TMN architecture.

The Appendix provides a description of the TMN architecture.

1.1.2.3 ENVIRONMENTAL ASSUMPTIONS

The following specific environmental conditions have been assumed in specifying the security mechanisms required to protect TMNs:

1 . Physical security - it is assumed that TMN components are in physically secure locations or that manual

procedures and controls and other physical safeguards (e.g., locked equipment cabinet) can provide

physical security for a given location.

2. Training and Awareness - these topics are viewed as part of the overall security strategy for a given

enviroiunent. Management must make an informed decision regarding the adequacy of existing training

and awareness efforts.

3. User Service Perspective - the security features of a given service or application are outside the scope

of this effort. This includes service specific, and fraud detection and prevention requirements.

4. There will be one or more personnel assigned to manage the system, including the security of the

information it contains.

5. If a network interface is supported, the attached networks will provide some facility to transport the

identity of remote users.

I.IJ DEFINITIONS

User

The term user refers to an individual, group, host, domain, trusted communication channel, network address/port,

another network, a remote system (e.g., operations system), or a process (e.g., service or program) that accesses

the netwoik, or is accessed by it, including any entity that accesses a network support entity to perform OAM&Prelated tasks. Regardless of their role, users must be required to successfully pass an identification and

authentication (I&A) mechanism. For example, I&A would be required for a security or system administrator.

For customers, I&A could be required for billing purposes.* See Figure 1

For some services (e.g.. Emergency Services) a customer may not need to be authenticated by the system.

5
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

Customer

The term customer applies to a person or organization who subscribes to a service offered by a telecommunications provider and is accountable for its use. A customer is permitted to use an NE to make calls and configure local line parameters (e.g., configure the numbers that should receive forwarded calls).'

Security Administrator

The term security administrator is used generically to mean the highly privileged role a person may have for

performing security-related administrative tasks (e.g., customize the audit features for the system).

SBFMCE

ADMINISTRATOR

Figure 1 - User Roles.

Domain

The term domain refers to a part of the network that is administered by a single authority.

1.1.4 AUDIENCE

The TSG targets four distinct audiences: users, vendors, evaluators and service providers.

* The TSG addresses the security needs oftelecommunications systems users. This includes application

developers, customers, and private sector and government administrators. The requirements focus on

the basic security requirements of commercial telecommunications systems.

* The TSG provides vendors with a single, well-defined set of security requirements that are applicable

In some circumstances a customer can also play the role of administrator, for example, when the customer has access to operations

information that would permit him to reconfigure his circuits. Some service providers offer this service, as well as other OAM&P features, to customers for a fee.

6
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

across their entire customer base. These requirements represent the integration of a number of security

requirement specifications fi"om various sources (see Section 1 . 1 .2.2.2) into a single set that is expected

to have wide acceptance. Vendors can more confidently use this set to develop a single system with

features that meet the needs of a significant customer base. The level of detail provided by these

requirements should help clarify what the vendor must do to comply.

* Product and system evaluators can apply the well-defined set of security requirements in the TSG to their work. The detailed level of the requirements significantly decrease the need for evaluator

interpretation. A format similar to that used in the Common Criteria provides a basis for widespread

acceptance of the requirements and mutual recognition of evaluations.

* Service providers are provided a clearly defined and widely accepted set of security requirements that are consistent with user expectations. It is anticipated that the TSG will result in a wider array of

competitively priced products fi-om which service providers can choose when responding to user

solicitations and requirements.

1.1.5 TERMINOLOGY

The TSG project adopts the following terminology used in the MSR document:

* Requirement - A feature or fimction that is necessary to satisfy the security needs of a typical

conmiercial or government organization. Failure to meet a Requirement may cause application

restrictions, result in improper functioning of the system, or hinder operations. A Requirement contains

the word shall and is identified by the letter "R."

* Advisory - A feature or function that mav be desired by a typical commercial or government

organization. An Advisory represents a goal to be achieved. An Advisory may be reclassified as a Requirement at some future date. An advisory contains the word should and is identified by the letter "A."

1.1.6 CONFORMANCE

Due to the hierarchical nature ofthe TMN architecture, different levels of conformance will be specified. At the network

corr^nent level, for example, conformance can be linked to the detailed analysis and evaluation of a particular element.

In situations where control is less definitive, conformance may need to be demonstrated in less rigorous ways. This would

be the case for network components that are controlled by an administrative entity that is distinct from the user environment, or where two TMNs need to be intercoimected.

1.1.7 APPLYING THE TSG

It is not sufficient to specify requirements in terms of features and functions. A framework for applying the requirements

is also included to provide additional guidance to users and vendors.

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

The TSG effort provides baseline criteria from which requirements specific to a particular TMN environment may be

derived. In addition, this baseline can assist the user in formulating a specific security policy. The baseline is a benchmark

with which formal security requirements for a specific TMN environment can be compared and exceptions justified on the

basis of unique vulnerabilities, associated risks, and sound business decisions. For some specific TMN environments the

baseline may have to be augmented with additional security features that are tied into the policy, as well as with the

identified security needs of the environment.

1.1.8 AREA FOR FURTHER RESEARCH

There is one area, broadband network components, that needs to be fiirther studied to determine whether the TSG applies

to these components also and, if so, where they fit in the series of documents. The broadband network area is evolving and

is in the early stages of network trials and product development. The initial versions of these broadband products may not

accurately represent what a broadband network node will look like in the fiiture. Some of these products, even though acting

in the role of a NE, may be more closely aligned with data communication equipment in terms of functionality. More work

is needed to determine if this is a new class of equipment that needs specific requirements or whether it fits into the existing

categories of equipment (i.e., NEs and data communication network nodes). This document, which focuses on NEs, MDs,

and EMs, is the initial phase of the TSG effort. The second phase will cover data communication network nodes.

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

2.0 SECURITY THREATS AND CONCERNS

2.1 INTRODUCTION

In the United States, government and industry have become dependent upon telecommunications networks to support commerce in all ofthe major economic sectors. At the same time, because of changes in technology, regulations, customer

service demands, and accelerated technology deployments to address market pressures, the Public Switched Network (PSN)

is becoming more vulnerable to security breaches.

Several reports have discussed recent intrusion experiences and potential threats to the PSN. The National Research Council

report, "Growing Vulnerability of the Public Switched Networic: Implications for National Security Emergency

Preparedness" [1], and the "Report of the Network Security Task Force" [2], both address growing concern with

possible network disruptions. A more recent study, "The Electronic Intrusion Threat To National Security and

Emergency Preparedness (NS/EP) Telecommunications" [18] reports that the network intruder's knowledge and

sophistication is increasing and the potential impact on the PSN is greater. Adequate protection of PSN resources is required

to ensure: the availability of service during emergencies; the integrity of transmitted information; the non-disclosure of

sensitive information; and the prevention of service fraud.

This chapter describes the scope of the threat, sources for these threats and characteristics associated with the major

categories of threats.

2.2 SCOPE OF SECURFIT THREATS

Changes in network architectures, technologies, interfaces, services, and operations may impact the ability of the PSN to provide the mix of functions and services to meet NS/EP and commercial needs. "Threats" are accidental or deliberate

actions or events that con^romise the quaUty, utiUty, or functionality of network services and operations. Threats can result

in financial losses for the network and service providers and/or their users. A "security threat" is an intentional threat,

whether mischievous or maUcious, against network services and operations. The focus of this document is security threats.

Threats to the PSN could result in any of the following impacts:

1 . Service denial or disruption - Typically, service disruptions caused by intruders have been brought about

by accidental actions rather than malicious attempts.

2. Unauthorized monitoring and disclosure of sensitive information - The current approaches that intruders

have used are eavesdropping techniques, network monitoring tools, and intrusions into network

databases containing customer information.

3. Unauthorized modification of user or network information and network services - Intruders have

changed user service profiles and affected billing and routing. This can result in unreliable service.

4. Fraud - The typical approach is to build upon the previous attacks and masquerade as a legitimate

customer to commit fraud related to voice and data services.

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

2.3 SOURCES OF THREATS

Threats to the PSN arise from several different sources:

Source Likelihood Principal Impact on Network

Employees/Insiders

Natural disasters

Hackers

65%

20%

15%

Availability, integrity, privacy

Availability

Availability, integrity, privacy

2.3.1 EMPLOYEES/INSIDERS

Intentional and accidental errors, omissions, and malicious acts by employees cause the majority of the damages and losses

experienced in the telecommunications industry. This is partly attributable to changes in the definition of "employee."

Previously, an employee was usually considered a full-time member of an organization. From a security perspective, it generally equated to an insider with high privilege. Today, insiders also include contractors who have administrative roles

with respect to network service and may perform other job functions as well. This broader definition of an employee

increases the potential of insider attacks that can severely impact the security of the PSN.

2.3.2 NATURAL DISASTERS

Natural disasters and accidents resulting Irom man-made causes can impact the availability of the PSN. Disasters such as hurricanes, floods, fire, etc., impact the timeliness and quality of the delivered services. In addition to the basic security concerns, NS/EP related capabilities can also be affected. Methods of dealing with threats fi-om natural and man-made

disasters include the use of redundant networks, reliable components, disaster recovery plans, and priority restoration of

services (e.g.. The Teleconmiunications Service Priority (TSP) System provides for priority provisioning and restoration

of NS/EP telecommunications services). A complete discussion of this topic is beyond the scope of this document.

2.3.3 MALICIOUS HACKERS

The PSN is becoming increasingly controlled and dependent on software and operations networks that may offer customer

access to network functions, user-configured databases, and special features. The potential for intruders to access network

management and operations functions is growing because customers now have greater access to fimctions that were

previously restricted to telecommunications employees. This increases threats caused by viruses, worms, and other

malicious software. Dial-in access to PSN components is a prime point of malicious intrusions into software-based

telecommunications systems.

The FCC-mandated ONA is designed to provide equal, user-transparent access via the PSN to network services provided

by network-based and non-network enhanced service providers. ONA has the potential to create network vulnerabilities

because it greatly increases the number of users (some of whom may be hostile) who have awareness of the network

architecture. See NIST Special Publication 800-1 1 [22] for more information on the impact of ONA. In addition, as users

learn more about the operation ofnetwork software, those with hostile intent will acquire knowledge that could assist them

in misusing resources.

Statistics - Datapro Research Corporation - figure in Security Overview 1, 14th NCSC, 1991; Wall Street Journal, Aug 15, 1990

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

2.4 THREAT CATEGORIES

Threats are circumstances or events with the potential to cause harm to a system in the form of destruction, disclosure, or

modification of data and/or denial of service. They have the potential to compromise the security of software applications

providing OAM&P fiinctionality as well as network services. They may be deliberate, e.g., hacking, or accidental, e.g. procedural errors. The following is a list of categories of threats to software applications residing on NE platforms:

1. Masquerade - an attempt to gain unauthorized access to, or greater privilege to a system, by posing as an authorized user (e.g., using stolen logon ids and passwords). This may be done by replaying data or

inserting false data that appears genuine into a communications path. System software and data may be

deleted, disclosed, or corrupted. An example is the re-programming of NE software to insert malicious

code to steal passwords. This threat can occur from:

a. Outside users accessing the NE ft-om the public network; ^ b Locally connected users;

c. Compromised administrator accounts that are configured for direct and remote access;

d. Administrators dialing into dial-in modems connected to the NE.

2. Disclosure of information - data disclosed without authorization, either by deliberate action or by

accident. Examples include:

a. Eavesdropping on phone conversations or on data transmissions;

b. Unauthorized disclosure of routing, address or other customer or service related information;

c. Deliberate misrouting data to enable an unauthorized entity to access information.

3. Message stream or data modification - data altered in some meaningful way by reordering, deleting or modifying it. Examples include:

a. Accessing and changing billing information;

b. Unauthorized modification of NE software or databases;

c. Rerouting calls.

4. Denial of service - actions that prevent the NE fi-om fimctioning in accordance with its intended purpose.

A piece of equipment or entity may be rendered inoperable or forced to operate in a degraded state; operations that depend on timeliness may be delayed. Examples include:

a. Unauthorized destruction of existing NE resources including hardware, software, and

databases;

b. Degraded NE service processing caused by a large volume of service requests;

c. Putting a NE in an "out-of-service" state.

5. Traffic analysis - a form of passive attack in which an intruder observes information being transmitted

and makes inferences fi-om the calling and called numbers, and the frequency and length of the calls. Examples are:

a. An intruder concludes that a high volume of communications between a company and the

Patent Office indicates that a patent is being filed;

b. A corporate merger is deduced from the amount of traffic between two companies.

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

3.0 REQUIREMENTS FRAMEWORK

This document specifies the generic security requirements for switching, access, and transport NEs. It applies to all new

NEs, as well as supporting entities called Element Managers (EMs) or Mediation Devices (MDs). Depending on local

policy decisions, existing systems (NEs, MDs, etc.) should be upgraded to meet these requirements. Although the term NE

is used exclusively in the following paragraphs, the requirements also apply to MDs and EMs. In addition, the document

pertains to software and data and is applicable through all phases of the product life cycle.

Future NEs must follow these requirements throughout their life cycle. Existing NEs, when major modification occurs, must incorporajte these life cycle requirements which will remain throughout the rest of their life cycle.

3.1 REQUIREMENTS APPLICABILITY

3.1.1 MEDIATION DEVICES AND ELEMENT MANAGERS

MDs and EMs manage network resources and provide a wide range of fimctions in support of the NE using different

interfaces. These devices may control various types of network services, provide for information conversion and storage,

perform protocol interworking, and manage network resources individually or in aggregation as a subnetwork. They may

perform operations-related functions for network resources, and/or may assist in handling calls. This is consistent with the

TMN architecture described in the Appendix.

The placement of fimctions into a physical system is an implementation decision made by the vendor. Consequently, the

security requirements for a particular implementation of a mediation device or element manager depend on the functionality

of the resident applications, and the associated risks. A risk analysis has to be performed to determine the specific NE

security requirements that apply. However, the High Level Security Requirements defined in Section 3.2 must be followed.

3.1.2 COMPONENT VIEW

This document addresses NE security. In a TMN environment there are security dependencies that must be considered.

TMN components interface with other components within the context of defined trust relationships. When securing a NE

or its interfaces, these dependencies need to be recognized.

3.1.3 SECURITY POLICY

A commercial unclassified security baseline (Section 4) is defined in this document. Additional security may be needed

to meet specific application and service needs. Senior level management must establish a security policy and define

mission critical requirements for a NE and its associated operating envirormient. -

3.1.4 USER ACCESS

New interfaces and user groups may require access to NEs. In particular, unbundling the PSN as defmed by the ONA,

and emerging customer network management services will affect NE security. The defined baseline requirements can be

used to derive specific poUcies, requirements, mechanisms and procedures to accommodate the increased diversity in user

access.

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

3.1.5 FRAUD

Fraud is a critical concern when providing user services. This document addresses fraud as viewed from the standpoint

of applying security requirements in an operations setting. The generic security requirements of this guideline protect

OAM«&P functions that may be used to commit fraud. Fraud of billable service capabilities is not addressed. The

requirements are not specific to particular billable services that could be susceptible to various types of attack (e.g.,

masquerade and unauthorized access).

3.1.6 NEW TECHNOLOGIES

New technologies and services, e.g., broadband, have resulted in various types of equipment being classified as NEs.

Besides the traditional large NEs residing in central office environments, smaller NEs can be located at the edges of the

PSN in various locations such as in private networks and user locations. A risk analysis will help identify security threats as well as the vulnerabiUties ofthe interfaces in such equipment. Although the High Level Security Requirements defined

in the next section are applicable, the detailed requirements in Chapter 4 may need to be modified to accommodate the

identified risks and vulnerabilities.

3.2 fflGH LEVEL SECURITY REQUIREMENTS

This section provides High Level Security Requirements for NEs. The statements (S) describe basic high level security

features. Each is followed by an appropriate high level policy guideline (P).

51. IDENTIFICATION

Identification is the process whereby the NE recognizes a user's unique and auditable identity such as the User-ID. The

User-ID is the name by which a valid user is recognized by the NE. This item of information is generally not considered

confidential.

PI . All authorized users of the NE shall be uniquely identified to support individual accountability.

52. AUTHENTICATION

Authentication is the process of verifying the claimed identity of the NE user. Passwords and smart cards can be used to provide this verification. Authentication information, especially when it is transmitted between a user and a remote NE,

must be kept confidential.

P2. The NE shall authenticate all users prior to initially allowing access.

53. SYSTEM ACCESS CONTROL

NE access control authorizes establishment, continuation, and completion of a session that is responsible for processing,

storing, or transmitting information. NE access is allowed only to those users that are identified and authenticated.

P3. The NE shall not allow access to users, processes, or other systems unless they are properly identified and authenticated.

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

54. RESOURCE ACCESS CONTROL

Resource access control provides the capability of denying access to NE resources in the absence of proper authorization.

Users may be restricted from executing unauthorized commands, or from accessing information in certain records and

fields. For the NE, security-critical functions must be restricted to users with special privileges. This is recommended to control the extent of damage that can be caused by mistakes or malicious actions. Users should possess no more privilege

than necessary to perform their job fixnction. This enforces the principle of least privilege.

P4. The NE shall assign and enforce levels of privilege to users, processes and other systems for restricting the use of

resources.

55. DATA AND SYSTEM INTEGRITY

Data and system integrity deals with consistency and reliability issues associated with the NE and its data and software

resources.

P5. The NE shall support mechanisms that ensure the integrity of the system and information stored, processed and

transmitted by the system.

56. AUDIT

An audit trail, which supports accountability, is required for a NE. Users should be prevented from modifying audit

information.

P6. The NE shall provide an audit log for investigating security relevant events.

57. SECURITY ADMINISTRATION

Security administration consists of secure management and management of security including proper activation,

maintenance, and use of NE security features. It entails tasks such as managing the security database, replacing vendorsupplied default passwords, and customizing the security audit features for OAM&P systems.

P7. The NE shall provide tools for managing security tasks for OAM&P systems by an authorized administrator.

58. DATA CONFIDENTIALITY

Data Confidentiality deals with protecting against the disclosure of information by ensuring that the data is limited to those

authorized or by representing the data in such a way that its semantics remain accessible only to those who possess some

critical information (e.g., a key for decrypting the enciphered data).

P8. The NE shall support mechanisms that ensure the confidentiality of sensitive information stored, processed and

transmitted by the system.

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

4.0 DETAILED GUIDELINE

Mechanisms that enforce telecommunications security policies and guard against security intrusions are required. Proper

controls will reduce security breaches and financial losses.

This section ofthe TSG provides baseUne security requirements for the NE portion of TMN. Requirements are listed for

Identification, Authentication, System Access Control, Resource Access Control, Data and System Integrity, Audit, Data

Confidentiality, and Security Administration. The requirements do not address unique security risks and vulnerabilities

of specific NE configurations, or particular network environments. The following terminology is used:

* Requirement (R) - A security feature that is necessary to ensure the correct functioning of an NE.

* Advisory (A) - A security feature that is desirable to ensure the correct functioning of an NE.

4.1 IDENTIFICATION

All authorized users must be uniquely identified to support individual accountabiUty. A user may be a person, a process, or some other system (e.g., an OS, another NE) that accesses or attempts to access the NE to perform tasks or process a

call. A user identification code (User-ID) is a non-confidential, unambiguous, and auditable representation of a user.

The requirements for Identification are:

Rl . Within a specific NE, the NE shall enforce unambiguous User-IDs to identify its users.'

R2. All NE interfaces and ports that accept user command inputs shall require unambiguous User-IDs before

performing any actions.

R3. The NE shall internally maintain the identity of all current active users.

R4 . The NE shall restrict a User-ID to only one active session.

R5. All operations-related processes running on the NE shall be associated with the User-ID of the invoking user.

R6. If a user-ID has not been used for a specified time interval, the NE shall be capable of disabling that User-ID.

In addition, the security administrator shall have a choice of automatic or manual disabling of these User-IDs.

4.2 AUTHENTICATION

Authentication is the process of verifying the claimed identity of a session requestor. The confidential authenticator that

provides the verification can be based on a password, Personal Identification Number (PIN), token, smart card, biometrics,

exchange of keys, etc.

The user may be a person, a system, another process, etc. When a process is invoked by another process, the invoked process shall be

associated with the ID of the invoking process. Autonomous processes shall have an associated identification code. The use of aliases is permitted only after a user has been properly identified and authenticated.

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

The requirements for Authentication are:

R7. The NE shall verify the identity of all users prior to allowing access.

R8. All NE interfaces and ports that accept user command inputs shall require user authentication before performing

R9. The NE shall ensure the confidentiality of all internally stored authentication data and protect it fi-om access by

unauthorized users.

RIO. Reusable passwords transmitted across networks, including wireless or other unprotected chaimels, shall be

encrypted.

Rl 1 . The NE shall preserve the confidentiality and integrity of stored authentication information such as passwords,

PINs, and authentication tokens.

R12. Authentication information entered during login shall be immediately overwritten within the NE.

R13. The NE shall not permit users to bypass the authentication mechanism.

R14, Only designated security administrators shall be able to access protected authentication information.

R15. The NE shall prohibit the outputting or writing of a clear text representation of authentication information to any

printer, terminal, or data entry device.

R16. The NE shall perform the entire authentication procedure even if an invalid User-ID is entered. The NE shall not

disclose which part of the authentication is incorrect and shall provide no information to the user other than

"invalid attempt."

RI7. If reusable passwords are used as the authentication mechanism, then:

a. Users shall not be notified if they select a password already associated with another user.

b. The NE shall permit users to change their passwords only if they have been properly authenticated to

any actions.

the system at the time they make the request.

c. After a password is assigned to a user, the user shall be required to immediately change the password

the first time the user establishes a session. Users that do not comply will not be allowed to continue the

session.

d. If passwords are used for authentication, the NE shall require a user selected password to have a minimum password length of 6 characters, use both alpha and numeric characters, and use both upper

and lower case characters. (See FIPS 112 and FIPS 181 for additional guidance on the selection of

passwords).

e. The NE shall require users to change passwords after a specified period of time. Users shall be

prevented ft"om choosing a password that they have previously used xmtil a specified period of time

elapses.

f. The security administrator shall have the capability of setting the password aging interval and reuse

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

period.

g. The NE shall notify users a specified period of time prior to expiration of their password.

h. The security administrator shall have the capability of setting this time period.

L Passwords shall not be transmitted in clear text.

Al . The NE should require those users who access the system remotely to use an authentication mechanism stronger

than a password.

A2. Users who perform critical administrative and other OAM&P functions should be authenticated by means of a procedure that is stronger than passwords; for example, a biometrics, token-based, or cryptographic technique.

A3. A NE should be able to incorporate and support authentication schemes including those based on trusted thirdparty servers that provide common dedicated services.

If the authentication mechanism uses public-key encryption technology based on third party servers, then:

a. Users' public keys should be certified by a trusted certification authority (CA) that protects the

association of users with their public keys.

b. Users' private keys should not be known by a CA. When a pair of keys are generated for a user, only

the public key needs to be shared with the CA.

c. The server should maintain a certificate revocation list (CRL) of all invalid/compromised keys, and

prevent the use of such keys.

If the authentication mechanism uses private-key technology based on third party servers, then:

a. The server should support secure registration and timely revocation procedures for user ID/key pairs.

b. The NE should support a secure repository of shared keys for users and services.

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4.3 SYSTEM ACCESS CONTROL

The NE must identify and authenticate the session requestor before granting permission to use the system. NE access

control mechanisms must provide the security features required for establishing and continuing a session.

The requirements for System Access Control are:

Rl 8. The NE shall not allow access to any user unless identified and authenticated. Only authorized users, processes

or remote systems shall be allowed access.

R19. All ports and interfaces of the NE that accept operations-related command inputs shall exercise access control.

This includes ports that provide direct, dial-up, and data communications network access.

R20. The NE shall not allow any session to be established via a port that is not designed to accept operations-related

command inputs.

R2 1 . The NE shall not provide any default User-IDs that can permit unauthenticated system access.

R22. The NE log-in procedure shall exit and end the session if the user authentication procedure is incorrectly

performed a specified number of times. This value shall be set by the security administrator.

R23 . Exceeding the threshold for incorrectly performing the user authentication procedure shall be considered a security

relevant event. The NE shall notify the security administrator in real time of this occurrence.

R24. When the threshold for incorrectly performing the user identification procedure has been exceeded, the NE shall lock out that log-in port for a specified interval of time.

R25. To prevent unauthorized users from purposely locking out all input ports by performing incorrect user

authentications, the default lock-out period shall not exceed 60 seconds. Only the security administrator shall be

able to modify that value.

R26. When the threshold for incorrectly performing the user authentication procedixre has been exceeded, the NE shall not suspend the associated User-ID. Suspension could allow an unauthorized user to disable all accounts.

R27. When a logical connection is established, but before access, the NE shall provide an advisory warning message

regarding unauthorized entry/use and its possible consequences. The message shall comply with applicable local,

state, and federal laws.

R28. Upon successful access to the NE, the system shall display for the user the date and time of the user's last successful access to the NE and the number of unsuccessful attempts.

R29. The NE shall automatically disconnect a user and require reauthentication after a specified period of inactivity.

The time-out interval shall be set by the security administrator.

R30. The NE shall end a session by means of a secure log-off procedure. The port shall be dropped irrmiediately if the

session is interrupted due to causes such as time-out, power failure, link discoimection, etc.

R3 1 . The NE shall be able to incorporate and support mechanisms to grant or deny access to any user based on time-ofday, day-of-week, and calendar date.

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

4.4 RESOURCE ACCESS CONTROL

The resource access control mechanism Hmits the use of NE resources, such as processes and databases, based on the

principle of "minimum privilege"; i.e., access is granted to only those resources that are needed to perform the job function.

Levels of access permission may be assigned to users, data entry devices, and NE ports for restricting the use of NE

resources.

The requirements for Resource Access Control are:

R32. The NE shall provide a level of granularity such that for each user allowed access to resources it shall be possible

to grant access rights to specific software, processes, databases, data, etc.

R33. Only authorized users shall be allowed access to software in the NE. Software shall be access controlled for

overwrite and update, as well as execution rights.

R34. Control of access to resources shall be based on authenticated user identification.

R35. The NE shall provide a level of granularity such that for each resource controlled by the NE it shall be possible

to:

1 . Grant access rights to a single user, group of users, or a port.

2. Deny access rights to a single user, group of users, or a port.

R36. The NE shall have the capability to screen access to specified resources and restrict a user's ability to perform

certain designated operations on the basis of originating address/port. Unauthorized addresses/ports shall be

denied access.

R37. Modification of the access rights to a resource shall be allowed only by the owner of that resource or by an

appropriate security administrator.

R38. The NE shall provide a mechanism to remove access rights to all resources for a user or a group of users.

R39. The NE shall protect the data files and tables associated with the access control mechanisms fi-om unauthorized

access.

R40. Users having predefined roles shall not have default rights to modify their roles and associated rights.

4.5 DATA AND SYSTEM INTEGRITY

Integrity ofboth the NE system and its data must be ensured. System integrity is concemed with issues related to providing an acceptable level of service. If service interruptions and degradation are not minimized, customers will lose confidence

in the system and supplier. Data integrity must be ensured during transmission/reception, processing, and storage of data.

The requirements for Data and System Integrity are:

R41 . The NE shall have the capability to identify the original creator of any named or user-accessible NE resources such as data and processes.

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

R42. The NE shall have the capability to identify the originator of any operations information received via

communications networks.

R43. The NE shall provide mechanisms that allow it to periodically validate its correct operation.

R44. The NE shall have the capability to protect the integrity of stored data by performing cryptographically-based

integrity checks (e.g., message authentication code) and/or data updates.

R45. The NE shall be designed and developed to protect data integrity by checking inputs for reasonable values.

R46. Documentation for the NE shall contain recommendations for running, on a regular basis, integrity checking

utilities for file systems and disks.

R47. A non-privileged user action, either deliberate or accidental, that requests NE resources shall not cause denial of

service of the NE to other users.

R48. Mechanisms shall be provided to allow the NE to recover from a failure or discontinuity without risk of

compromising security.'"

R49. To facilitate recovery, and to reduce the potential in:q)act of a security compromise, check points shall be included

in the software.

R50. The NE shall provide mechanisms to preserve the integrity of data stored internally to the NE.

R5 1 . The NE shall have the capability to verify the integrity of new software releases and subsequent patches.

R52. The NE shall process security alarms in real-time based on indicated severity levels.

4.6 AUDIT

The audit log provides the capability to investigate unauthorized activities after they occur so that proper remedial action can be taken. The requirements for Audit are:

R53. The NE shall generate logs that contain information about security relevant events. Items selected for recording

shall be defined and selected by the security administrator. The logs shall enable security administrators to

investigate losses and improper actions on the part of users, legitimate and otherwise, and to seek legal remedies.

R54. The NE shall provide audit cq)abilities with user accountability for all significant events. The user-identification

associated witfi any request or activity shall be maintained and passed on to any other connected systems so that

the initiating user can be traceable for the lifetime of the request or activity.

R55. The audit log shall be protected from unauthorized access or destruction by means of access controls based on

user and channel privileges.

R56. The audit log and audit control mechanisms shall be protected from modification or destruction.

For example, if the system is halted to download new or modified software, or a system restart is required.

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

R57. The audit log and audit control mechanisms shall survive system restarts by being maintained throughout a system

restart.

R58. Subject to selections made by the security administrator, the audit log shall minimally record information on the

following events:

1. Changes to the NE security configuration.

2. Modifications of NE software.

3. Invalid user authentication attempts.

4. Unauthorized attempts to access resources such as data, the password file, and transactions.

5. Changes to a user's security profile and attributes.

R59. For each recorded event, the audit log shall record the following:

1. Type of event.

2. Date and time of event.

3. User identification including associated terminal, port, network address, or communication device.

4. Names of the resources accessed.

5. Success or failure of the event.

R60. The security administrator shall be immediately notified if the audit log fails to record the events that are required

to be recorded.

R61. It shall not be possible to disable the audit log of actions taken by a security administrator.

R62. Authentication information such as passwords, PINs, and cryptographic keys shall not be recorded in the security

log.

R63. In order to prevent overwriting any information, the NE shall be capable of automatically forwarding the audit

log to a storage device or authorized management system. Any transmission of audit information shall be done

securely.

R64. When the audit log is copied to other media or locations, the copy shall start at the oldest record and copy

sequentially without deleting any records.

R65. The NE shall support audit analysis tools that can produce exception reports, summary reports, and detailed

reports on specific data items, users, or communication facilities.

4.7 SECURITY ADMINISTRATION

Security administration mechanisms enable a human administrator to control the security of an NE.

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This administrator must
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

have proper authorization to perform security administration fiinctions such as setting security parameters, removing default

values, and updating security features.

The requirements for Security Administration are:

R66. The NE shall separate administrator functions from other user functions. Only authorized security administrators

shall be allowed to execute these functions.

R67. The security functions performed by authorized administrators shall be identified and documented.

R68. The NE shall provide a mechanism for an authorized administrator to display all currently active users or software

processes. These processes include both OAM&P and telecommunications service applications.

R69. The NE shall provide a mechanism for an authorized administrator to be able to independently and selectively

review the action of any one or more users, including privileged users, based on individual user identity. Note:

due to privacy considerations, users must be aware that this capability exists. (See CSL Bulletin, "Guidance on

the Legality of Keystroke Monitoring," March 1993.)

R70. The NE shall provide a mechanism that permits an authorized administrator to monitor the activities of a specific

terminal, port or network address in real time. (See note in R69)

R71. The NE shall provide a mechanism to allow an authorized administrator to lock out a specific port or channel.

R72. The NE shall provide a mechanism to allow an authorized administrator to authorize or revoke users.

R73. The NE shall provide a mechanism to allow an authorized administrator to identify all resources owned by or

accessible to any specific user along with the associated access privileges.

R74. The NE shall provide a mechanism to allow an authorized administrator to create a unique User-ID for a particular

user.

R75. The NE shall provide a mechanism to allow an authorized administrator to disable User-IDs after a specified

period of time during which the user-ID has not been used.

R76. The NE shall provide a mechanism to allow an authorized administrator to reinstate or delete a disabled User-ID.

R77. The NE shall provide a mechanism to allow an authorized administrator to enter, reset, or delete passwords for

users.

R78. An authorized administrator shall not be able to retrieve any password in clear text.

R79. The NE shall provide the capability to generate alarms for specifiable security events. The alarms shall be

prioritized based on pre-determined criteria and routed to the security administrator. Only an authorized security

administrator can deactivate an alarm.

R80. The following security parameters shall be specifiable and adjustable by an authorized security administrator:

1 . The period after which a password must be changed.

2. The interval during which an expired password shall be unselectable as a new password by the same

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

user.

3. The threshold on the number ofincorrect login attempts which, when exceeded, would cause immediate

notification.

4. The duration of channel lock-out that occurs when the threshold on the number of incorrect logins is exceeded.

5. A customized advisory warning banner that is displayed upon system entry regarding unauthorized use, and the possible consequences of violating the warning.

6. The duration ofthe inactivity time-out interval for an established session.

7. The access rights of a user to a resource.

8. The events that may trigger alarms (e.g., failed login attempts), the levels of alarms (e.g., critical,

major, minor, etc.), the type of notification (e.g., bell and/or message), and the routing of the alarm

(e.g. , specific port).

9. Parameters for the mechanism that notifies users of the need to change passwords shall be specifiable

and adjustable by an authorized administrator. This includes how far in advance users shall be notified,

and the grace period for using an expired password.

R81. The NE shall provide a mechanism to allow an authorized administrator to periodically validate the correct operation of the NE with respect to the supported applications.

4^ DATA CONFIDENTIALITY

There are conditions where the confidentiality of data must be ensured. Data Confidentiality should be ensured during

transmission/reception, processing, and storage of data.

The requirements for Data Confidentiality are:

R82. The type of data items and structures whose confidentiality is protected shall be identified. For example,

if data is transmitted, some identifier might accompany the transaction which would identify the key

and related attributes needed by the receiving system.

R83. The system shall have the capability of protecting the confidentiality of each individual message or

selective fields of each message.

R84. The NE shall support mechanisms that ensure the confidentiality of communication information by

encryption if the communication media cannot be protected by physical and administrative means.

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TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

5.0 DEVELOPMENT LIFE CYCLE REQUIREMENTS

NE security features are not sufficient by themselves to provide a secure NE. Security has to be considered throughout the

life cycle of the NE. Security features and mechanisms need to be properly conceived, designed, implemented, tested,

installed, documented, and maintained.

This section describes generic security requirements for the various phases of the NE development life cycle. The purpose

is to ensure the development ofNE security features with reliability, integrity and robustness. In addition, vendor support

is necessary to ensure NE security.

5.1 SECURITY POLICY

R85. The NE vendor shall have a security policy that governs software development, integrity, and maintenance

throughout the life cycle of the NE product.

5.2 REQUIREMENTS ANALYSIS

R86. Security requirements shall consist of the baseline security features described in Section 4.

R87. For specific applications, it may be necessary to perform a risk analysis to determine if additional measures commensurate with the relative threats, vulnerabilities, and values of the resources (application) being protected

are needed. This risk analysis shall include:

a. Nature of NE data, software, and functions used by the application.

b. Potential risk if the security baseline is not followed.

c. Impact on NE data, software, and fimctions if they are compromised on the NE or associated systems

and networks.

5.3 SYSTEM DESIGN

R88. The design shall not allow for a mode of entry that is not a documented feature.

R89. The functional requirements shall be based on the application requirements defined during the requirements

analysis phase.

R90. The functional requirements shall be documented.

R91 . The design shall accommodate the various roles that a user may take on when accessing the NE.

R92. The security fimctions available to be performed by an appropriate administrator shall be identified and

documented.

R93 . If there is a feature to support the enabling and disabling of a privileged account, the software fimctions shall not

allow a user with limited privilege to become a highly privileged user in any context, except with administrator

24
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

intervention.

R94 Limited-privilege users shall not be able to access the underljdng software operating environment unless that

environment can support the defined access control policies and the user is given the higher privilege by

administrator action.

5.4 DETAILED SYSTEM DESIGN

R95. The design shall specify security mechanisms, based on the target operating environment and supported

applications, to satisfy the functional requirements.

R96. The specified security mechanisms shall be documented.

R97. The design review process shall address the functional requirements as well as the potential for unintended

security flaws and malicious attacks.

5.5 IMPLEMENTATION

R98. Security mechanisms defined in the detailed design shall be implemented.

R99. No method of NE access, including access for software debugging, shall be provided other than what was

designed and documented.

RIOO. Passwords used during the design and implementation phases shall not be stored in cleartext in unprotected

databases or files.

RlOl. If a password is used in cleartext form in an executing process, the password shall be overwritten inmiediately

after use within the NE.

R102. NE software shall be treated as proprietary and labeled with appropriate markings. These markings shall reside

with the software when it is in the NE and when the software is listed in any documentation.

5.6 DEVELOPMENT ENVIRONMENT

R103. NE vendors shall have documented security policies that address the secure use and maintenance of the computer

systems and software used in the development of the NE.

R104. All systems and software used in developing the NE shall be subject to periodic security audits.

R105. Passwords, and other forms of personal authentication, used by key software developers and other privileged

users, shall be protected and subject to appropriate complexity requirements.

R106. Passwords used during the development phase shall not be stored in clear text in unprotected databases,

workstations, or networks.

R107. Third party (e.g., commercial software vendor) software used in NE development shall be obtained in an

authorized manner with appropriate approvals.

25
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

R108. Public domain and other types of commonly available software (free-ware, share-ware etc.) shall not be used in

NE development unless the software has been inspected, in source form, by an approved authority.

Rl 09. Software that is developed internally by a vendor for use in NE development shall be approved by an appropriate

authority within the development environment.

5.7 SYSTEM TEST

Rl 1 0. All security features shall be tested for flaws by the vendor. The tests shall be conducted under conditions that

simulate normal use as well as emphasizing penetration attacks that target the software security features.

Rl 1 1. Security flaws detected during testing shall be corrected, removed, or neutralized and the software retested to demonstrate that the flaws have been eliminated and that no new flaws have been introduced.

Rl 12. The vendor's test plan, procedures, suites, and results shall be verified and documented by an independent vendor

testing group.

5.8 PACKAGING AND DELIVERY

Rl 13. Only authorized software and software modifications shall be added to the software baseline to form the product

baseline.

Rl 14. All software changes shall be tested, verified, documented and reviewed to determine that NE security has not

been compromised.

Rl 15. There shall be tools and procedures to generate a new version of the NE software from backup media or source

code.

Rl 1 6. There shall be tools and procedures for verifying that a software release contains all of the appropriate component

modules.

R117. There shall be tools and procedures for protecting the backup media and source code from unauthorized

modification.

Rl 1 8. The master copy of all routines used to generate the NE software shall be logically, physically, and procedurally

protected from unauthorized modification and destruction.

Rl 19. The vendor shall maintain a master database of all delivered software releases by release number.

R120. All NE software shall be delivered with secure installation defaults."

R121. Passwords associated with default User-IDs delivered with a NE software release shall be modifiable by the

administrator during the installation process.

R122. The NE vendor shall provide procedures that enable the user to conduct a site security acceptance test that

For example, audit features should be enabled, default accounts should be password protected, etc.

26
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

demonstrates conformance to the security requirements.

R123. The user shall be provided with tools and procedures to verify, at any time, that the currently installed software

has remained consistent with the delivered software, i.e., no unauthorized modifications.

R124. Vendor documentation shall be delivered with the distributed software.

5.9 DOCUMENTATION

R125. Instructions for and descriptions of security features and items for consideration shall be provided for all of the

NE users, including administrators and operators.

R126. The documentation shall have the appropriate proprietary markings.

R127. General user documentation shall not contain any information that could compromise NE security if publicly

disclosed. Actual passwords shall not be listed in the documents.

R128. A User Guide that describes all security features, and provides guidelines on their use, shall be provided.

R129. There shall be a System Administration Guide that contains:

1 . Description of security features and protection considerations for securing the NE;

2. Description of security tools used to examine the security of the NE and guidelines on the use of these

tools;

3. Recommendations for configuring the security related parameters of the NE software;

4. Guidelines on the administrator functions and activities needed to secure the NE;

5. ' Guidelines on security self-assessment techniques to assess and maintain NE security.

6. Guidelines on monitoring and maintaining the availability of the NE and its resources to detect and

prevent denial of service attacks and to maintain the integrity of security features (e.g., log space to record system activity).

R130. The System Operations Guide shall describe procedures to initially start the NE in a secure manner and to restart and recover the NE after various system events.

R1 3 1 . Documentation shall be distributed through authorized charmels

27
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

5.10 SUPPORT

Rl 32. The vendor shall identify a primary and secondary point of contact for addressing and resolving issues related to the security of the NE.

Rl 33. The vendor shall have a documented method for notifying users of new or recurring security problems.

R134. All problems that pose a security threat to the NE shall be prioritized and addressed in the order of highest threat

to the NE.

R135. If security problems are identified by the vendor in a supported release, the vendor shall make that information

available to authorized user representatives in a protected fashion.

R136. If possible, security fixes to identified security problems shall not require the installation of the next release of

the NE software.

R137. All user login information and access configurations shall be protected by the vendor and treated in a restricted manner.

Rl 38. Vendor personnel shall not access the NE, either remotely or on the user's site, without prior authorization from

the user.

Rl 39. Vendor persormel accessing an NE shall not bypass user security procedures.

R140. All new software features and patches shall be tested first on a development system and approved by an

appropriate testing organization, prior to installation on an operational system.

R141 . Tests that modify live data shall not be performed.

R142. A risk analysis shall be conducted of proposed software changes to determine their impact on NE security.

R143. Any changes to security features or security defaults shall be documented and made available to the user before

the software is distributed.

R144. All maintenance and feature releases shall be subject to the entire set of development life cycle requirements.

R145. Documentation shall be provided that describes the secure administration, operation and use of new software

features and fixes.

i

28
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

LIST OF ACRONYMS

CA Certification Authority

ccnr Comite Consultatif International Telegraphique et Telephonique

CPE Customer Premise Equipment

CRL Certificate Revocation List

DCN Data Communications Network

EM Element Manager

FCC Federal Communications Commission

I&A Identification and Authentication

ISDN Integrated Service Digital Network

MD Mediation Device

NE Network Element

NISI National Institute of Standards and Technology

NOF Network Operations Forum

NS/EP National Security and Emergency Preparedness

NSTAC National Security Telecommunications Advisory Committee

OAM&P Operations, Administration, Maintenance, and Provisioning

ONA Open Network Architecture

OS Operations System

PBX Private Branch Exchange

PIN Personal Identification Number

PSN Public Switched Network

SONET Synchronous Optical Network

STP Signal Transfer Point

TCSEC Trusted Computer System Evaluation Criteria

TMN Telecommunications Management Network

TSG Telecommunications Security Guideline

WS Workstation

29
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

REFERENCES

[I] National Research Council. Growing Vulnerability of the Public Switched Networks. National Academy Press,

1989.

[2] National Security Telecommunications Advisory Committee. Report of the Network Security Task Force. National Security Telecommunications Advisory Committee, 1990.

[3] Federal Communications Commission. Computer Inquiry III. FCC, June 1986.

[4] S.E. Dolan. Open Network Architecture from an Operational Perspective. In IEEE Globecom. IEEE, 1988.

[5] L. Simpson. Open Networic Architecture: 0AM Perspective, an RBOC's View. In IEEE Globecom. IEEE, 1988.

[6] G. Giridharagopal S. Homayoon. ONA: Demands on Provisioning and Performance. In IEEE Globecom. IEEE,

1988.

[7] F.S. Dworak. Approaches to Detecting and Resolving Feature Interactions. In Proceedings, IEEE Globecom.

IEEE, 1991.

[8] Installation and Maintenance Responsibilities - SS7 Link and Trunk Installation and Maintenance Access

Services: Network Operations Forum Reference Document, Issue 3, Jan 1993.

[9] Generic Requirements for Network Element Security. Technical Report TR-NWT-000815, Issue 2, Bellcore,

1992.

[ 1 0] Bellcore Operations System Security Requirements. Technical Report TA-STS-001 1 94, Bellcore, 1 99 1

.

[II] Bellcore Standard Operating Environment Security Requirements. Technical Report TA-STS-00 1 080, Bellcore,

1990.

[12] NISTIR 5153, Minimum Security Requirements for Multi-User Operating Systems. March 1993.

[13] CSL Bulletin, Guidance on the Legality of Keystroke Monitoring. March 1993

[14] Bellcore Technical Advisory, TA-NWT-001469, Issue 1, September 1993, Generic Requirements on Security for

OSI-Based Telecommunications Management Network Interfaces.

[15] Bellcore Technical Reference, TR-NWT-000815, Issue 2, December 1992, Network Element (NE) Memory

Administration - Network Element and Network System Security.

[ 1 6] CCITT Recommendation M.3 0 1 0, Principles for a Telecommunications Management Network.

[ 1 7] American National Standard for Telecommunications; Operations. Administration. Maintenance, and Provisioning

(OAM&P") - Principles of Functions. Architectures and Protocols for Telecommunications Management Network

(TMNt Interfaces ANSI T 1.2 10. 1993.

[18] Office of the Manager, National Communications Systems, The Electronic Intrusion Threat to National Security

30
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

and Emergency Preparedness fNS/EP") Telecommunications: An Awareness Document. Second Edition,

December 5, 1994.

NCS Manual 3-1-1, Telecommunications Service Priority (TSP) System for National Security Emergency

Preparedness rNS/EP) Service User Manual. July 9, 1990.

American National Standard for Telecommunications; Operations. Administration. Maintenance, and Provisioning

(OAMScP) - Baseline Security Requirements for Telecommunications Management Network (TMN"). ANSI

Tl.243, 1995.

American National Standard for Telecommunications, Security Framework for Telecommunications Management

Network (TMN). ANSI Tl.233-1993.

NIST SP 800-1 1. The Impact ofthe FCC's Open Network Architecture on NS/NP Telecommunications Security.

February, 1995.

CCITT Recommendation X.700, Management framework definition for Open Systems Interconnection (OSD

for CCITT applications.

31
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

APPENDIX

1.0 GUIDING NETWORK ARCHITECTURE

The Telecommunication Security Guideline ( TSG) effort is guided by the Telecommunication Management Network

(TMN) architecture as specified in CCITT and ANSI documents (See Figure 2, TMN Logical Network)

TMNs provide an organized architecture to interconnect various types of operations oriented application systems and/or

telecommunications network equipment. The architecture permits information exchange by means of standardized

interfaces, protocols and messages.

A TMN exchanges management information among the various TMN components. Within the context of the TMN,

management refers to a set of capabilities to allow for the exchange and processing of management information to assist

administrators in conducting their business efficiently.

A TMN can vary in complexity from a simple connection between an Operations System (OS) and a single piece of

telecommunications equipment to a complex network interconnecting many different types of OSs and telecommunications

equipment. The component parts of a TMN include:

* Operations Systems (OS) - Systems that perform operations fiinctions, i.e., activities required to provide

the services of a telecommunications system to users/subscribers. The OS supports the processing of

information related to operations, administration, maintenance, and provisioning (OAM&P) for

telecommunications networks.

* Network Elements (NE) - Analog and digital devices and supporting equipment that provide

communication services such as switching, multiplexing, and transport services to subscribers. NEs also

support network maintenance, billing and administration functions.

* Data Communication Networks (DCN) - Communication networks within TMNs that transport

information related to telecommunication management between function blocks. These function blocks,

in various TMN components, provide the general functions to perform OAM&P (See Figure 2). In its simplest form, a DCN may be a point-to-point connection.

* Mediation Devices (MD) - Devices that act on the content of information passing between network

elements and operations systems. MDs may provide any of the following: upper layer protocol

internetworking, adaptation, filtering, format conversion, storage, thresholding, condensing information,

and decision making.

* Workstations (WS) - Collections of hardware and software that perform workstation functions, i.e., provide a human user with entry into or exit from a TMN component such as a NE or OS. A personal

computer (PC) or computer terminal can function as a workstation.

* Q Adapters (QA) - Devices that act on the content of information passing between TMN function blocks

and non-TMN function blocks. Protocols carrying the information may be converted. QAs also support

interfaces between TMN components and OSs and NEs that belong to the same jurisdiction as the TMN

but do not conform to TMN standards.

32
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

1.1 DISTINCTION BETWEEN OSs AND NEs

Traditionally the major distinction between OSs and NEs has been that NEs forward switch and transport information

between subscribers of the network while OSs do not perform any activities on a per call basis. This distinction is fading

with the emergence of network systems that assist in call handling; for example, 800 number translation databases that do

not carry any user information.

NEs interact essentially through signaling for call setup and disconnect. In this situation there is no direct exchange of

management information between NEs (though NEs participate in the transport of such information between OSs and NEs).

Future developments may result in NEs, such as Synchronous Optical Network (SONET) digital cross connects, that

exchange management information (not related to any specific call) to execute circuit rearrangements.

Different performance requirements for NEs and OSs generally exist. Communications involving NEs are usually more

time critical since they involve the allocation and availabiUty of network resources and hence the quality of service as seen by the end users. By contrast, the exchange of management information by an OS is usually less time critical.

OSs perform functions such as surveillance, testing, performance monitoring, provisioning, and traffic management. The

OSs and NEs interface with people through end-user systems such as terminals and workstations (WS). The OSs and NEs

may also interface with external entities (OSs and WSs that are outside the TMN). Such interfaces, as well as some

interfaces that are internal to the TMN, may go through a Mediation Device (MD) or an NE acting in the role of a gateway.

1.2 DATA COMMUNICATIONS NETWORK (DCN)

The OSs and NEs, as well as the workstations, are interconnected via a Data Communications Network (DCN). The DCN

provides information transport mechanisms, including routing functions based on layers 1 through 3 of the OSI Reference

Model (i.e., physical, data link, and network layers).

Figure 2 illustrates the general relationship between a TMN and a telecommunications network that it manages. A TMN

is conceptually a separate network that interfaces a telecommunications network at several different points to send/receive

information to/fi'om it and to control its operations. The telecommunications network consists primarily of NEs that are organized to support services invoked by telecommunications-enabled user devices (e.g., telephones). A TMN may use

parts of the telecommunications network to provide its communications and to enable management of the TMN.

33
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

TMN Operations Operations Operations

System System System

Data Communications Network

. Transmission

B<change

Transmission

B(change

System System Bcchange

Telecommunication Network

Figure 2 - TMN Logical Network (General Relationship of a TMN to a Telecommunications

Network).

It is important to realize that a TMN only depicts a network environment that is under the control of one administrative

domain. Later phases of the TSG effort will embrace the security issues that arise when TMNs are interconnected.

1.3 FIELD OF APPLICATION

The following are examples of the networks, telecommunications services and major types of equipment that may be

managed by the TMN:

* Public and private networks, including ISDNs, mobile networks, private voice networks, private virtual

networks and advanced intelligent networks;

* TMN itself;

34
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

* Transmission terminals (multiplexers, cross connects, channel translation equipment, etc.);

* Digital and analog transmission systems (cable, fiber, radio, satellite, etc.);

* Operations systems and their peripherals;

* Mainframes, fi"ont-end processors, cluster controllers, file servers, etc.;

* Digital and analog exchanges;

* Area networks (WAN, MAN, LAN);

* Circuit and packet switched networks;

* Signaling terminals and systems including signal transfer points (STPs) and real time data bases;

* Bearer services and teleservices;

* PBXs, PBX accesses and user (customer) terminals;

* ISDN user terminals in accordance with relevant maintenance procedures for public networks;

* Software provided by or associated with telecommunications services, e.g., switching software,

directories, message data bases, etc.;

* Software applications running within mainfiames, etc. (including applications supporting TMN);

* Associated support systems (test modules, power systems, air conditioning units, building alarms

systems, etc.).

In addition, a TMN may be used to manage distributed entities and services offered by grouping items in the above list.

1.4 BASIC OBJECTIVES FOR THE TMN

The objective for the TMN specifications is to provide a fimiework for telecommimications management. By introducing

the concept ofgeneric network models for management, it is possible to perform general management of diverse equipment

using generic information models and standard interfaces.

The principle ofkeeping the TMN logically distinct fi-om the networks and services being managed introduces the prospect

of distributing the TMN fimctionality for centralized or decentralized management implementations. This means that

operators can perform management of a wide range of distributed equipment, networks and services from a number of

management systems.

Security and distributed data integrity are recognized as fiindamental requirements for the definition of a generic

architecture. A TMN may allow access and control from sources considered outside the TMN (e.g., inter-TMN

cooperation and network user access). Security mechanisms may be needed at various levels (managing systems,

coirmiunications fimctions, etc.)

1.5 FUNCTIONS ASSOCIATED WITH A TMN

35
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

A TMN is intended to support a wide variety of management areas that cover the planning, installation, operations,

administration, maintenance and provisioning of telecommunications networks and services.

The specification and development of the required range and functionality of applications to support the above management

areas is a local matter. Some guidance, however, is provided by CCITT which has categorized management into five broad

management functional areas (Recommendation X.700[23]). These areas provide a framework within which the

appropriate applications can be determined with respect to support for the administration's business needs. The

management functional areas are:

* Performance Management;

* Fault Management;

* Configuration Management;

* Accounting Management;

* Security Management.

Some of the information that is exchanged within the TMN may be used in support of more than one management area. The classification of the information exchange within the TMN is independent of the use that will be made of the

information.

Overall the functionality of the TMN consists of the ability to:

* Exchange management information across the boundary between the telecommunications environment

and TMN environment;

* Convert management information from one format to another so that management information flowing

within the TMN environment has a consistent nature;

* Transfer management information between locations within the TMN environment;

* Analyze and react appropriately to management information;

* Manipulate management information into a form that is useful and/or meaningful to the management

information user;

* Deliver management information to the management information user and to present it with the

appropriate representation;

* Ensure secure access to management information by authorized management information users.

1.6 ARCHITECTURAL REQUIREMENTS

The TMN needs to be aware of telecommunications networks and services as collections of cooperating systems. The

architecture is concerned with orchestrating the management of individual systems to have a coordinated effect upon the

network. Introduction of TMNs gives administration the possibility to achieve a range of management objectives, including

the ability to:
TELECOMMUNICATION SECURITY GUIDELINES FOR TMN

* Minimize management reaction times to network events;

* Minimize load caused by management traffic where the telecommunications network is used to carry

it;

* Allow for geographic dispersion of control over aspects of the network operation;

* Provide control mechanisms to minimize security risks;

* Provide control mechanisms to locate and contain network faults;

* Improve service assistance and interaction with customers.

To take into account at least the above objectives, the TMN architecture should:

* Make various implementation strategies and degree of distribution ofmanagement functionality possible;

* Allow for management ofheterogeneous networks, equipment and services within a telecommunications

enviroimient;

* Allow for compartmented structure, where management functions may operate autonomously within the

compartment;

* Allow for technological and functional changes;

* Include migration capabilities to enhance early implementation and allow future refinement;

* Provide a certain degree of reliability and security in the support of management functions;

* Make it possible for customers, value added service providers, and other domain administrations to access management functions;

* Make it possible to have different, or the same, management applications at different locations, even if they access the same NE;

* Address the requirements of small and large numbers of managed objects;

* Make the interworking between separately managed networks possible, so that inter-network services can be provided between domains;

* Provide for management of hybrid networks consisting of mixed network equipment;

* Allow flexibiUty in the degree of reliability/cost trade-off in all the network management components.

-^US. GOVERNMENT FMNTING OFHCE: IMS - 4M-525/479U 37

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