CRITICAL 

INFRASTRUCTURE 

PROTECTION 

Challenges and Efforts to 

Secure Control Systems 

Statement of Robert F. Dacey, 

Director, Information Security Issues 

United States General Accounting Office 

GAO Testimony

Before the Subcommittee on Technology 

Information Policy, Intergovernmental 

Relations and the Census, House 

Committee on Government Reform

For Release on Delivery 

Expected at 2 p.m. EST 

Tuesday, March 30, 2004 

GAO-04-628T 
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and methodology, click on the link above. 

For more information, contact Robert F. 

Dacey at (202) 512-3317 or daceyr@gao.gov. 

Highlights of GAO-04-628T, a testimony 

before the Subcommittee on Technology, 

Information Policy, Intergovernmental 

Relations and the Census, House 

Committee on Government Reform 

March 30, 2004

CRITICAL INFRASTRUCTURE 

PROTECTION 

Challenges and Efforts to Secure Control 

Systems 

In addition to general cyber threats, which have been steadily increasing, 

several factors have contributed to the escalation of the risks of cyber 

attacks against control systems. These include the adoption of standardized 

technologies with known vulnerabilities and the increased connectivity of 

control systems to other systems. Typical control system components are 

illustrated in the graphic below. Control systems can be vulnerable to a 

variety of attacks, examples of which have already occurred. Successful 

attacks on control systems could have devastating consequences, such as 

endangering public health and safety.

Securing control systems poses significant challenges, including limited 

specialized security technologies and lack of economic justification. The 

government, academia, and private industry have initiated efforts to 

strengthen the cybersecurity of control systems. The President’s National 

Strategy to Secure Cyberspace establishes a role for DHS to coordinate with 

these entities to improve the cybersecurity of control systems. While some 

coordination is occurring, DHS’s coordination of these efforts could 

accelerate the development and implementation of more secure systems. 

Without effective coordination of these efforts, there is a risk of delaying the 

development and implementation of more secure systems to manage our 

critical infrastructures. 

Typical Components of a Control System 

Source: GAO (analysis), Art Explosion (clipart). 

Engineering 

workstation

Supervisory control and 

monitoring station

Control System

Enterprise network Internet/business partners

A control 

system may 

have multiple 

remote/local 

stations.

Handheld device

Remote/local station N

Sensor Sensor

Control 

equipment

Control 

equipment

Controller

Remote/local station 1

Sensor Sensor

Control 

equipment

Control 

equipment

Controller

Handheld device

Human-machine 

interface (HMI) Redundant 

application 

servers

Modem Modem

Communications network can be the Internet, a public switched 

telephone network, a wireless network, or a hardwired network.

Computerized control systems 

perform vital functions across 

many of our nation’s critical 

infrastructures. For example, in 

natural gas distribution, they can 

monitor and control the pressure 

and flow of gas through pipelines. 

In October 1997, the President’s 

Commission on Critical 

Infrastructure Protection 

emphasized the increasing 

vulnerability of control systems to 

cyber attacks. At the request of the 

House Committee on Government 

Reform, Subcommittee on 

Technology, Information Policy, 

Intergovernmental Relations and 

the Census, this testimony will 

discuss GAO’s March 2004 report 

on potential cyber vulnerabilities, 

focusing on (1) significant 

cybersecurity risks associated with 

control systems (2) potential and 

reported cyber attacks against 

these systems (3) key challenges to 

securing control systems, and 

(4) efforts to strengthen the 

cybersecurity of control systems. 

In a March 2004 report, GAO 

recommends that the Secretary of 

the Department of Homeland 

Security (DHS) develop and 

implement a strategy for 

coordinating with the private 

sector and other government 

agencies to improve control 

system security, including an 

approach for coordinating the 

various ongoing efforts to secure 

control systems. DHS concurred 

with GAO’s recommendation. 
Page 1 GAO-04-628T 

Mr. Chairman and Members of the Subcommittee: 

I am pleased to be here today to participate in the Subcommittee’s hearing 

on the cyber vulnerabilities in industrial control systems. Control 

systems—which include supervisory control and data acquisition 

(SCADA) systems and distributed control systems1

—perform vital 

functions across many of our nation’s critical infrastructures, including 

electric power generation, transmission, and distribution; oil and gas 

refining and pipelines; water treatment and distribution; chemical 

production and processing; railroads and mass transit; and manufacturing. 

In October 1997, the President’s Commission on Critical Infrastructure 

Protection highlighted the risk of cyber attacks as a specific point of 

vulnerability in our critical infrastructures, stating that “the widespread 

and increasing use of SCADA systems for control of energy systems 

provides increasing ability to cause serious damage and disruption by 

cyber means.” 

In my testimony today I will discuss the results of our recent report, which 

is being released today.2

 As you requested, this report identifies 

(1) significant cybersecurity risks associated with control systems, 

(2) potential and reported cyber attacks against these systems, (3) key 

challenges to securing control systems, and (4) efforts to strengthen the 

cybersecurity of control systems. 

In preparing our report, we analyzed research studies and reports, as well 

as prior GAO reports and testimonies on critical infrastructure protection 

(CIP), information security, and national preparedness, among others. We 

analyzed documents from and met with private-sector and federal officials 

who had expertise in control systems and their security. Our work was 

performed from July 2003 to March 2004 in accordance with generally 

accepted government auditing standards. 

 

1

Control systems are computer-based systems that are used by many infrastructures and 

industries to monitor and control sensitive processes and physical functions. Typically, 

control systems collect sensor measurements and operational data from the field, process 

and display this information, and relay control commands to local or remote equipment. 

There are two primary types of control systems. Distributed Control Systems (DCS) 

typically are used within a single processing or generating plant or over a small geographic 

area. Supervisory Control and Data Acquisition (SCADA) systems typically are used for 

large, geographically dispersed distribution operations. 

2

U.S. General Accounting Office, Critical Infrastructure Protection: Challenges and 

Efforts to Secure Control Systems, GAO-04-354 (Washington, D.C.: March 15, 2004). 
Page 2 GAO-04-628T 

Results in Brief 

For several years, security risks have been reported in the control systems 

on which many of the nation’s critical infrastructures rely to monitor and 

control sensitive processes and physical functions. In addition to a steady 

increase in general cyber threats, several factors have contributed to the 

escalation of risks specific to control systems, including the (1) adoption 

of standardized technologies with known vulnerabilities, (2) connectivity 

of control systems with other networks, (3) insecure remote connections, 

and (4) widespread availability of technical information about control 

systems. 

Control systems can be vulnerable to a variety of types of cyber attacks 

that could have devastating consequences—such as endangering public 

health and safety; damaging the environment; or causing a loss of 

production, generation, or distribution by public utilities. Control systems 

have already been subject to a number of cyber attacks, including attacks 

on a sewage treatment system in Australia in 2000 and, more recently, on a 

nuclear power plant in Ohio. 

Securing control systems poses significant challenges. These include the 

limitations of current security technologies in securing control systems, 

the perception that securing control systems may not be economically 

justifiable, and conflicting priorities within organizations regarding the 

security of control systems. 

Government, academia, and private industry have initiated several efforts 

that are intended to improve the security of control systems. These 

initiatives include efforts to promote the research and development of new 

technologies, the development of requirements and standards, an 

increased awareness and sharing of information, and the implementation 

of effective security management programs. The President’s National 

Strategy to Secure Cyberspace establishes a role for the Department of 

Homeland Security (DHS) to coordinate with the private sector and other 

governments to improve the cybersecurity of control systems. While some 

coordination is occurring, DHS’s coordination of these efforts could 

accelerate the development and implementation of more secure systems. 

Without adequate coordination of these efforts, there is a risk of delaying 

the development and implementation of more secure systems to manage 

our critical infrastructures. 

In our March report, we recommend that the Secretary of DHS develop 

and implement a strategy for coordinating with the private sector and 
Page 3 GAO-04-628T 

other government agencies to improve control system security, including 

developing an approach for coordinating the various ongoing efforts to 

secure control systems. This strategy should also be addressed in the 

comprehensive national infrastructure plan that the department is tasked 

to complete by December 2004. DHS’s concurred with our 

recommendation and agreed that improving the security of control 

systems against cyberattack is a high priority. 

Background 

Cyberspace Introduces Risks for Control Systems 

Dramatic increases in computer interconnectivity, especially in the use of 

the Internet, continue to revolutionize the way our government, our 

nation, and much of the world communicate and conduct business. The 

benefits have been enormous. Vast amounts of information are now 

literally at our fingertips, facilitating research on virtually every topic 

imaginable; financial and other business transactions can be executed 

almost instantaneously, often 24 hours a day, and electronic mail, Internet 

Web sites, and computer bulletin boards allow us to communicate quickly 

and easily with an unlimited number of individuals and groups. 

However, this widespread interconnectivity poses significant risks to the 

government’s and our nation’s computer systems and, more important, to 

the critical operations and infrastructures they support. For example, 

telecommunications, power distribution systems, water supplies, public 

health services, national defense (including the military’s warfighting 

capability), law enforcement, government services, and emergency 

services all depend on the security of their computer operations. If they 

are not properly controlled, the speed and accessibility that create the 

enormous benefits of the computer age may allow individuals and 

organizations to eavesdrop on or interfere with these operations from 

remote locations for mischievous or malicious purposes, including fraud 

or sabotage. Table 1 summarizes the key threats to our nation’s 

infrastructures, as observed by the Federal Bureau of Investigation (FBI). 
Page 4 GAO-04-628T 

Table 1: Threats to Critical Infrastructures Observed by the FBI 

Threat Description 

Criminal groups There is an increased use of cyber intrusions by criminal groups who attack 

systems for monetary gain. 

Foreign intelligence services Foreign intelligence services use cyber tools as part of their information 

gathering and espionage activities. 

Hackers Hackers sometimes crack into networks for the thrill of the challenge or for 

bragging rights in the hacker community. While remote cracking once required a 

fair amount of skill or computer knowledge, hackers can now download attack 

scripts and protocols from the Internet and launch them against victim sites. 

Thus, while attack tools have become more sophisticated, they have also 

become easier to use. 

Hacktivists Hacktivism refers to politically motivated attacks on publicly accessible Web 

pages or e-mail servers. These groups and individuals overload e-mail servers 

and hack into Web sites to send a political message. 

Information warfare Several nations are aggressively working to develop information warfare 

doctrine, programs, and capabilities. Such capabilities enable a single entity to 

have a significant and serious impact by disrupting the supply, communications, 

and economic infrastructures that support military power—impacts that, 

according to the Director of Central Intelligence, can affect the daily lives of 

Americans across the country.a

Insider threat The disgruntled organization insider is a principal source of computer crimes. 

Insiders may not need a great deal of knowledge about computer intrusions 

because their knowledge of a victim system often allows them to gain 

unrestricted access to cause damage to the system or to steal system data. The 

insider threat also includes outsourcing vendors. 

Virus writers Virus writers are posing an increasingly serious threat. Several destructive 

computer viruses and “worms” have harmed files and hard drives, including the 

Melissa macro virus, the Explore.Zip worm, the CIH (Chernobyl) virus, Nimda, 

and Code Red. 

Source: Federal Bureau of Investigation, unless otherwise indicated. 

a

Prepared statement of George J. Tenet, Director of Central Intelligence, before the 

Senate Select Committee on Intelligence, February 2, 2000. 

Government officials remain concerned about attacks from individuals 

and groups with malicious intent, such as crime, terrorism, foreign 

intelligence gathering, and acts of war. According to the FBI, terrorists, 

transnational criminals, and intelligence services are quickly becoming 

aware of and using information exploitation tools such as computer 

viruses, Trojan horses, worms, logic bombs, and eavesdropping sniffers 

that can destroy, intercept, degrade the integrity of, or deny access to 
Page 5 GAO-04-628T 

data.3 In addition, the disgruntled organization insider is a significant 

threat, because these individuals often have knowledge about the 

organization and its system that allows them to gain unrestricted access 

and inflict damage or steal assets without knowing a great deal about 

computer intrusions. As larger amounts of money and more sensitive 

economic and commercial information are exchanged electronically, and 

as the nation’s defense and intelligence communities increasingly rely on 

standardized information technology (IT), the likelihood increases that 

information attacks will threaten vital national interests. 

As the number of individuals with computer skills has increased, more 

intrusion or “hacking” tools have become readily available and relatively 

easy to use. A hacker can download tools from the Internet and literally 

“point and click” to start an attack. Experts agree that there has been a 

steady advance in the level of sophistication and effectiveness of attack 

technology. Intruders quickly develop attacks to exploit vulnerabilities 

that have been discovered in products, use these attacks to compromise 

computers, and share them with other attackers. In addition, they can 

combine these attacks with other forms of technology to develop 

programs that automatically scan networks for vulnerable systems, attack 

them, compromise them, and use them to spread the attack even further. 

From 1995 through 2003, the CERT Coordination Center4

 (CERT/CC) 

reported 12,946 security vulnerabilities that resulted from software flaws. 

Figure 1 illustrates the dramatic growth in security vulnerabilities over 

these years. The growing number of known vulnerabilities increases the 

potential for attacks by the hacker community. Attacks can be launched 

against specific targets or widely distributed through viruses and worms. 

 

3

Virus: a program that “infects” computer files, usually executable programs, by inserting a 

copy of itself into the file. These copies are usually executed when the “infected” file is 

loaded into memory, allowing the virus to infect other files. Unlike the computer worm, a 

virus requires human involvement (usually unwitting) to propagate. Trojan horse: a 

computer program that conceals harmful code. A Trojan horse usually masquerades as a 

useful program that a user would wish to execute. Worm: an independent computer 

program that reproduces by copying itself from one system to another across a network. 

Unlike computer viruses, worms do not require human involvement to propagate. Logic 

bomb: in programming, a form of sabotage in which a programmer inserts code that causes 

the program to perform a destructive action when some triggering event occurs, such as 

termination of the programmer’s employment. Sniffer: synonymous with packet sniffer. A 

program that intercepts routed data and examines each packet in search of specified 

information, such as passwords transmitted in clear text. 

4

The CERT/CC is a center of Internet security expertise at the Software Engineering 

Institute, a federally funded research and development center operated by Carnegie Mellon 

University. 
Page 6 GAO-04-628T 

Figure 1: Security Vulnerabilities, 1995–2003 

Along with these increasing vulnerabilities, the number of computer 

security incidents reported to CERT/CC has also risen dramatically—from 

9,859 in 1999 to 82,094 in 2002 and to 137,529 in 2003. And these are only 

the reported attacks. The Director of the CERT Centers has estimated that 

as much as 80 percent of actual security incidents goes unreported, in 

most cases because (1) there were no indications of penetration or attack, 

(2) the organization was unable to recognize that its systems had been 

penetrated, or (3) the organization was reluctant to report. Figure 2 shows 

the number of incidents that were reported to the CERT/CC from 1995 

through 2003. 
Page 7 GAO-04-628T 

Figure 2: Computer Security Incidents, 1995–2003 

According to the National Security Agency (NSA), foreign governments 

already have or are developing computer attack capabilities, and potential 

adversaries are developing a body of knowledge about U.S. systems and 

methods to attack these systems. The National Infrastructure Protection 

Center (NIPC) reported in January 2002 that a computer belonging to an 

individual who had indirect links to Osama bin Laden contained computer 

programs that indicated that the individual was interested in the structural 

engineering of dams and other water-retaining structures. The NIPC report 

also stated that U.S. law enforcement and intelligence agencies had 

received indications that Al Qaeda members had sought information about 

control systems from multiple Web sites, specifically on water supply and 

wastewater management practices in the United States and abroad. 

Since the terrorist attacks of September 11, 2001, warnings of the potential 

for terrorist cyber attacks against our critical infrastructures have 

increased. For example, in his February 2002 statement for the Senate 

Select Committee on Intelligence, the Director of Central Intelligence 
Page 8 GAO-04-628T 

discussed the possibility of a cyber warfare attack by terrorists.5 He stated 

that the September 11 attacks demonstrated the nation’s dependence on 

critical infrastructure systems that rely on electronic and computer 

networks. Further, he noted that attacks of this nature would become an 

increasingly viable option for terrorists as they and other foreign 

adversaries become more familiar with these targets and the technologies 

required to attack them. James Woolsey, a former Director of Central 

Intelligence, shares this concern, and on October 29, 2003, in a speech 

before several hundred security experts, he warned that the nation should 

be prepared for continued terrorist attacks on our critical infrastructures. 

Moreover, a group of concerned scientists warned President Bush in a 

letter that “the critical infrastructure of the United States, including 

electrical power, finance, telecommunications, health care, transportation, 

water, defense and the Internet, is highly vulnerable to cyber attack. Fast 

and resolute mitigating action is needed to avoid national disaster.” 

According to a study by a computer security organization, during the 

second half of 2003, critical infrastructure industries such as power, 

energy, and financial services experienced high attack rates.6

 Further, a 

study that surveyed over 170 security professionals and other executives 

concluded that, across industries, respondents believe that a large-scale 

cyber attack in the United States will be launched against their industry by 

mid-2006. 

What Are Control Systems? 

Control systems are computer-based systems that are used within many 

infrastructures and industries to monitor and control sensitive processes 

and physical functions. Typically, control systems collect sensor 

measurements and operational data from the field, process and display 

this information, and relay control commands to local or remote 

equipment. In the electric power industry, control systems can manage 

and control the generation, transmission, and distribution of electric 

power— for example, by opening and closing circuit breakers and setting 

thresholds for preventive shutdowns. Employing integrated control 

systems, the oil and gas industry can control the refining operations at a 

plant site, remotely monitor the pressure and flow of gas pipelines, and 

control the flow and pathways of gas transmission. Water utilities can 

 

5

Testimony of George J. Tenet, Director of Central Intelligence, before the Senate Select 

Committee on Intelligence, February 6, 2002. 

6

Symantec, Symantec Internet Security Threat Report: Trends for July 1, 2003-December 

31, 2003 (March 2004). 
Page 9 GAO-04-628T 

remotely monitor well levels and control the wells’ pumps; monitor flows, 

tank levels, or pressure in storage tanks; monitor water quality 

characteristics—such as pH, turbidity, and chlorine residual; and control 

the addition of chemicals. Control systems also are used in manufacturing 

and chemical processing. Control systems perform functions that vary 

from simple to complex; they can be used simply to monitor processes—

for example, the environmental conditions in a small office building—or to 

manage most activities in a municipal water system or even a nuclear 

power plant. 

In certain industries, such as chemical and power generation, safety 

systems are typically implemented in order to mitigate a potentially 

disastrous event if control and other systems should fail. In addition, to 

guard against both physical attack and system failure, organizations may 

establish backup control centers that include uninterruptible power 

supplies and backup generators. 

There are two primary types of control systems. Distributed Control 

Systems (DCS) typically are used within a single processing or generating 

plant or over a small geographic area. Supervisory Control and Data 

Acquisition (SCADA) systems typically are used for large, geographically 

dispersed distribution operations. For example, a utility company may use 

a DCS to generate power and a SCADA system to distribute it. Figure 3 

illustrates the typical components of a control system. 
Page 10 GAO-04-628T 

Figure 3: Typical Components of a Control System 

Source: GAO (analysis), Art Explosion (clipart). 

The enterprise network services 

all of the enterprise's business 

operations. Users on the network 

typically can access the Internet 

or business partner networks. 

Enterprises often integrate their 

control systems with their 

enterprise networks.

The supervisory control and 

monitoring station typically 

contains redundant application 

servers, an engineering 

workstation, and a humanmachine interface (HMI) that 

collects and logs information 

obtained from the remote/local 

stations and sends commands 

to the remote/local stations in 

response to events detected by 

the sensors. The HMI displays 

status information, including 

alarms needing operator 

attention.

A remote/local station contains 

a remote terminal unit (RTU), 

programmable logic controller 

(PLC), or other controller that 

receives and interprets the 

signals from the sensors and 

generates corresponding 

control signals that it transmits 

to the control equipment.

Workstations

Application 

server

Firewall

Redundant 

application 

servers

Hub/switch

Human-machine

interface (HMI) Engineering 

workstation

Enterprise 

network

Supervisory 

control and 

monitoring 

station

Control System

Remote/local station 1

Outside world

(may include vendors, customers, 

and other business partners)

Internet/business partners

Communications network can be the Internet, a public switched 

telephone network, a wireless network, or a hardwired network.

RTU, PLC, 

or other 

controller

A control system may 

have multiple 

remote/local stations.

(See note.)

Handheld device

Sensor Sensor

Control 

equipment

Control 

equipment

Printer

Modem

Remote/local station N

RTU, PLC, 

or other 

controller

Handheld device

Sensor Sensor

Control 

equipment

Control 

equipment

Modem

Note: Remote/local stations can include one or more interfaces to allow field operators to perform 

diagnostic and maintenance operations. Sensors can measure level, pressure, flow, current, 

voltages, etc., depending on the infrastructure. Control equipment can be valves, pumps, relays, 

circuit breakers, etc., also depending on the infrastructure. 

A control system typically is made up of a “master” or central supervisory 

control and monitoring station consisting of one or more human-machine 

interfaces where an operator can view status information about the 

remote/local sites and issue commands directly to the system. Typically, 

this station is located at a main site, along with application servers and an 

engineering workstation that is used to configure and troubleshoot the 

other components of the control system. The supervisory control and 
Page 11 GAO-04-628T 

monitoring station typically is connected to local controller stations 

through a hard-wired network or to a remote controller station through a 

communications network—which could be the Internet, a public switched 

telephone network, or a cable or wireless (e.g., radio, microwave, or 

Wi-Fi7

) network. Each controller station has a remote terminal unit (RTU), 

a programmable logic controller (PLC), or some other controller that 

communicates with the supervisory control and monitoring station. 

The control system also includes sensors and control equipment that 

connect directly with the working components of the infrastructure—for 

example, pipelines, water towers, or power lines. The sensor takes 

readings from the infrastructure equipment—such as water or pressure 

levels, electrical voltage or current—and sends a message to the 

controller. The controller may be programmed to determine a course of 

action and send a message to the control equipment instructing it what to 

do—for example, to turn off a valve or dispense a chemical. If the 

controller is not programmed to determine a course of action, the 

controller communicates with the supervisory control and monitoring 

station and relays instructions back to the control equipment. The control 

system also can be programmed to issue alarms to the operator when 

certain conditions are detected. Handheld devices, such as personal digital 

assistants, can be used to locally monitor controller stations. Experts 

report that technologies in controller stations are becoming more 

intelligent and automated and are able to communicate with the 

supervisory central monitoring and control station less frequently, thus 

requiring less human intervention. 

Control Systems Are at Increasing Risk 

Historically, security concerns about control have been related primarily 

to protecting them against physical attack and preventing the misuse of 

refining and processing sites or distribution and holding facilities. 

However, more recently, there has been a growing recognition that control 

systems are now vulnerable to cyber attacks from numerous sources, 

including hostile governments, terrorist groups, disgruntled employees, 

and other malicious intruders. 

In October 1997, the President’s Commission on Critical Infrastructure 

Protection discussed the potential damaging effects on the electric power 

 

7

Wi-Fi (short for wireless fidelity) is the popular term for a high-frequency wireless local 

area network. 
Page 12 GAO-04-628T 

and oil and gas industries of successful attacks on control systems.8

Moreover, in 2002, the National Research Council identified “the potential 

for attack on control systems” as requiring “urgent attention.”9

 In the first 

half of that year, security experts reported that 70 percent of energy and 

power companies experienced at least one severe cyber attack. In 

February 2003, the President clearly demonstrated concern about “the 

threat of organized cyber attacks capable of causing debilitating disruption 

to our Nation’s critical infrastructures, economy, or national security,” 

noting that “disruption of these systems can have significant consequences 

for public health and safety” and emphasizing that the protection of 

control systems has become “a national priority.”10

Several factors have contributed to the escalation of risk to control 

systems, including (1) the adoption of standardized technologies with 

known vulnerabilities, (2) the connectivity of control systems to other 

networks, (3) insecure remote connections, and (4) the widespread 

availability of technical information about control systems. 

Control Systems Are Adopting Standardized Technologies with Known Vulnerabilities 

In the past, proprietary hardware, software, and network protocols made 

it difficult to understand how control systems operated—and therefore 

how to hack into them. Today, however, to reduce costs and improve 

performance, organizations have been transitioning from proprietary 

systems to less expensive, standardized technologies such as Microsoft’s 

Windows, Unix-like operating systems, and the common networking 

protocols used by the Internet. These widely-used, standardized 

technologies have commonly known vulnerabilities, and sophisticated and 

effective exploitation tools are widely available and relatively easy to use. 

As a consequence, both the number of people with the knowledge to wage 

attacks and the number of systems subject to attack have increased. Also, 

common communication protocols and the emerging use of extensible 

markup language (commonly referred to as XML) can make it easier for a 

hacker to interpret the content of communications among the components 

of a control system. 

 

8

President’s Commission on Critical Infrastructure Protection, Critical Foundations: 

Protecting America’s Infrastructures (Washington, D.C.: October 1997). 

9

The National Research Council, Making the Nation Safer: the Role of Science and 

Technology in Countering Terrorism (Washington, D.C.: December 2002). 

10The White House, The National Strategy to Secure Cyberspace (Washington, D.C.: 

February 2003). 
Page 13 GAO-04-628T 

Control Systems Are Connected to Other Networks 

Enterprises often integrate their control systems with their enterprise 

networks. This increased connectivity has significant advantages, 

including providing decision makers with access to real-time information 

and allowing engineers to monitor and control the process control system 

from different points on the enterprise network. In addition, the enterprise 

networks are often connected to the networks of strategic partners and to 

the Internet. Furthermore, control systems are increasingly using wide 

area networks and the Internet to transmit data to their remote or local 

stations and individual devices. This convergence of control networks 

with public and enterprise networks potentially creates further security 

vulnerabilities in control systems. Unless appropriate security controls are 

deployed in both the enterprise network and the control system network, 

breaches in enterprise security can affect the operation of control systems. 

Insecure Connections Exacerbate Vulnerabilities 

Vulnerabilities in control systems are exacerbated by insecure 

connections. Organizations often leave access links—such as dial-up 

modems to equipment and control information—open for remote 

diagnostics, maintenance, and examination of system status. If such links 

are not protected with authentication or encryption, the risk increases that 

hackers could use these insecure connections to break into remotely 

controlled systems. Also, control systems often use wireless 

communications systems, which are especially vulnerable to attack, or 

leased lines that pass through commercial telecommunications facilities. 

Without encryption to protect data as it flows through these insecure 

connections or authentication mechanisms to limit access, there is little to 

protect the integrity of the information being transmitted. 

Information about Infrastructures and Control Systems Is Publicly Available 

Public information about infrastructures and control systems is readily 

available to potential hackers and intruders. The availability of this 

infrastructure and vulnerability data was demonstrated last year by a 

George Mason University graduate student who, in his dissertation, 

reportedly mapped every business and industrial sector in the American 

economy to the fiber-optic network that connects them, using material 

that was available publicly on the Internet—and not classified. 

In the electric power industry, open sources of information—such as 

product data and educational videotapes from engineering associations—

can be used to understand the basics of the electrical grid. Other publicly 
Page 14 GAO-04-628T 

available information—including filings of the Federal Energy Regulatory 

Commission (FERC), industry publications, maps, and material available 

on the Internet—is sufficient to allow someone to identify the most heavily 

loaded transmission lines and the most critical substations in the power 

grid. Many of the electric utility officials who were interviewed for the 

National Security Telecommunications Advisory Committee’s Information 

Assurance Task Force’s Electric Power Risk Assessment expressed 

concern over the amount of information about their infrastructure that is 

readily available to the public. 

In addition, significant information on control systems is publicly 

available—including design and maintenance documents, technical 

standards for the interconnection of control systems and RTUs, and 

standards for communication among control devices—all of which could 

assist hackers in understanding the systems and how to attack them. 

Moreover, there are numerous former employees, vendors, support 

contractors, and other end users of the same equipment worldwide who 

have inside knowledge about the operation of control systems. 

Security experts have stated that an individual with very little knowledge 

of control systems could gain unauthorized access to a control system 

using a port scanning tool and a factory manual that can be easily found 

on the Internet and that contains the system’s default password. As noted 

in the following discussion, many times these default passwords are never 

changed. 

Cyber Threats to Control Systems 

There is a general consensus—and increasing concern—among 

government officials and experts on control systems about potential cyber 

threats to the control systems that govern our critical infrastructures. As 

components of control systems increasingly make vital decisions that 

were once made by humans, the potential effect of a cyber attack becomes 

more devastating. Cyber threats could come from numerous sources 

ranging from hostile governments and terrorist groups to disgruntled 

employees and other malicious intruders. Based on interviews and 

discussions with representatives from throughout the electric power 

industry, the Information Assurance Task Force of the National Security 

Telecommunications Advisory Committee concluded that an organization 

with sufficient resources, such as a foreign intelligence service or a wellsupported terrorist group, could conduct a structured attack on the 
Page 15 GAO-04-628T 

electric power grid electronically, with a high degree of anonymity, and 

without having to set foot in the target nation. 

In July 2002, NIPC reported that the potential for compound cyber and 

physical attacks, referred to as “swarming attacks,” was an emerging 

threat to the critical infrastructure of the United States. As NIPC reports, 

the effects of a swarming attack include slowing or complicating the 

response to a physical attack. For instance, a cyber attack that disabled 

the water supply or the electrical system, in conjunction with a physical 

attack, could deny emergency services the necessary resources to manage 

the consequences of the physical attack—such as controlling fires, 

coordinating response, and generating light. 

According to the National Institute of Standards and Technology (NIST), 

cyber attacks on energy production and distribution systems—including 

electric, oil, gas, and water treatment, as well as on chemical plants 

containing potentially hazardous substances—could endanger public 

health and safety, damage the environment, and have serious financial 

implications such as loss of production, generation, or distribution by 

public utilities; compromise of proprietary information; or liability issues. 

When backups for damaged components are not readily available (e.g., 

extra-high-voltage transformers for the electric power grid), such damage 

could have a long-lasting effect. I will now discuss potential and reported 

cyber attacks on control systems, as well as challenges to securing them. 

Control Systems Can Be Vulnerable to Cyber Attacks 

Entities or individuals with malicious intent might take one or more of the 

following actions to successfully attack control systems: 

• disrupt the operation of control systems by delaying or blocking the flow 

of information through control networks, thereby denying availability of 

the networks to control system operators; 

• make unauthorized changes to programmed instructions in PLCs, RTUs, or 

DCS controllers, change alarm thresholds, or issue unauthorized 

commands to control equipment that could potentially result in damage to 

equipment (if tolerances are exceeded), premature shutdown of processes 

(such as prematurely shutting down transmission lines), or even disabling 

control equipment; 

• send false information to control system operators either to disguise 

unauthorized changes or to initiate inappropriate actions by system 

operators; 
Page 16 GAO-04-628T 

• modify the control system software, producing unpredictable results; and 

• interfere with the operation of safety systems. 

In addition, in control systems that cover a wide geographic area, the 

remote sites often are not staffed and may not be physically monitored. If 

such remote systems were to be physically breached, attackers could 

establish a cyber connection to the control network. 

Department of Energy (DOE) and industry researchers have speculated on 

how the following potential attack scenario could affect control systems in 

the electricity sector. Using war dialers11 to find modems connected to the 

programmable circuit breakers of the electric power control system, 

hackers could crack passwords that control access to the circuit breakers 

and could change the control settings to cause local power outages and 

even damage equipment. A hacker could lower settings from, for example, 

500 amperes12 to 200 on some circuit breakers; normal power usage would 

then activate, or “trip,” the circuit breakers, taking those lines out of 

service and diverting power to neighboring lines. If, at the same time, the 

hacker raised the settings on these neighboring lines to 900 amperes, 

circuit breakers would fail to trip at these high settings, and the diverted 

power would overload the lines and cause significant damage to 

transformers and other critical equipment. The damaged equipment would 

require major repairs that could result in lengthy outages. 

Control system researchers at DOE’s national laboratories have developed 

systems that demonstrate the feasibility of a cyber attack on a control 

system at an electric power substation where high-voltage electricity is 

transformed for local use. Using tools that are readily available on the 

Internet, they are able to modify output data from field sensors and take 

control of the PLC directly in order to change settings and create new 

output. These techniques could enable a hacker to cause an outage, thus 

incapacitating the substation. 

Experts in the water industry consider control systems to be among the 

primary vulnerabilities of drinking water systems. A technologist from the 

water distribution sector has demonstrated how an intruder could hack 

into the communications channel between the control center of a water 

distribution pump station and its remote units, located at water storage 

 

11War dialers are simple personal computer programs that dial consecutive phone numbers 

looking for modems. 

12An ampere is a unit of measurement for electric current. 
Page 17 GAO-04-628T 

and pumping facilities, to either block messages or send false commands 

to the remote units. Moreover, experts are concerned that terrorists could, 

for example, trigger a cyber attack to release harmful amounts of water 

treatment chemicals, such as chlorine, into the public’s drinking water. 

Cyber Attacks on Control Systems Have Been Reported 

Experts in control systems have verified numerous incidents that have 

affected control systems. Reported attacks include the following: 

• In 1994, the computer system of the Salt River Project, a major water and 

electricity provider in Phoenix, Arizona, was breached. 

• In March 1997, a teenager in Worcester, Massachusetts, remotely disabled 

part of the public switching network, disrupting telephone service for 600 

residents and the fire department and causing a malfunction at the local 

airport. 

• In the spring of 2000, a former employee of an Australian company that 

develops manufacturing software applied for a job with the local 

government, but was rejected. Over a 2-month period, the disgruntled 

rejected employee reportedly used a radio transmitter on as many as 46 

occasions to remotely hack into the controls of a sewage treatment system 

and ultimately release about 264,000 gallons of raw sewage into nearby 

rivers and parks. 

• In the spring of 2001, hackers mounted an attack on systems that were 

part of a development network at the California Independent System 

Operator, a facility that is integral to the movement of electricity 

throughout the state. 

• In August 2003, the Nuclear Regulatory Commission confirmed that in 

January 2003, the Microsoft SQL Server worm—otherwise known as 

Slammer—infected a private computer network at the Davis-Besse nuclear 

power plant in Oak Harbor, Ohio, disabling a safety monitoring system for 

nearly 5 hours. In addition, the plant’s process computer failed, and it took 

about 6 hours for it to become available again. Slammer reportedly also 

affected communications on the control networks of at least five other 

utilities by propagating so quickly that control system traffic was blocked. 

In addition, in 1997, the Department of Defense (DOD) undertook the first 

systematic exercise to determine the nation’s and DOD’s vulnerability to 

cyberwar. During a 2-week military exercise known as Eligible Receiver, 

staff from NSA used widely available tools to show how to penetrate the 

control systems that are associated with providers of electric power to 

DOD installations. Other assessments of control systems at DOD 
Page 18 GAO-04-628T 

installations have demonstrated vulnerabilities and identified risks in the 

installations’ network and operations. 

Securing Control Systems Poses Significant Challenges 

The control systems community faces several challenges to securing 

control systems against cyber threats. These challenges include (1) the 

limitations of current security technologies in securing control systems, 

(2) the perception that securing control systems may not be economically 

justifiable, and (3) the conflicting priorities within organizations regarding 

the security of control systems. 

Lack of Specialized Security Technologies for Control Systems 

According to industry experts, existing security technologies, as well as 

strong user authentication and patch management practices, are generally 

not implemented in control systems because control systems usually have 

limited processing capabilities, operate in real time, and are typically not 

designed with cybersecurity in mind. 

Existing security technologies13 such as authorization, authentication, 

encryption, intrusion detection, and filtering of network traffic and 

communications, require more bandwidth, processing power, and memory 

than control system components typically have. Controller stations are 

generally designed to do specific tasks, and they often use low-cost, 

resource-constrained microprocessors. In fact, some control system 

devices still use the Intel 8088 processor, which was introduced in 1978. 

Consequently, it is difficult to install current security technologies without 

seriously degrading the performance of the control system. 

For example, complex passwords and other strong password practices are 

not always used to prevent unauthorized access to control systems, in part 

because this could hinder a rapid response to safety procedures during an 

emergency. As a result, according to experts, weak passwords that are 

easy to guess, shared, and infrequently changed are reportedly common in 

control systems, including the use of default passwords or even no 

password at all. 

 

13 See U.S. General Accounting Office, Information Security: Technologies to Secure 

Federal Systems, GAO-04-467 (Washington, D.C.: March 9, 2004) for a discussion of 

cybersecurity technologies. 
Page 19 GAO-04-628T 

In addition, although modern control systems are based on standard 

operating systems, they are typically customized to support control system 

applications. Consequently, vendor-provided software patches may be 

either incompatible with the customized version of the operating system 

or difficult to implement without compromising service by shutting down 

“always-on” systems or affecting interdependent operations. Another 

constraint on deploying patches is that support agreements with control 

system vendors often require the vendor’s approval before the user can 

install patches. If a patch is installed in violation of the support agreement, 

the vendor will not take responsibility for potential impacts on the 

operations of the system. Moreover, because a control system vendor 

often requires that it be the sole provider of patches, if the vendor delays 

in providing patches, systems remain vulnerable without recourse. 

Information security organizations have noted that a gap exists between 

currently available security technologies and the need for additional 

research and development to secure control systems. Research and 

development in a wide range of areas could lead to more effective 

technologies. For example, although technologies such as robust firewalls 

and strong authentication can be employed to better segment control 

systems from external networks, research and development could help to 

address the application of security technologies to the control systems 

themselves. Other areas that have been noted for possible research and 

development include identifying the types of security technologies needed 

for different control system applications, determining acceptable 

performance trade-offs, and recognizing attack patterns for use in 

intrusion detection systems. 

Industry experts have identified challenges in migrating system 

components to newer technologies while maintaining uninterrupted 

operations. Upgrading all the components of a control system can be a 

lengthy process, and the enhanced security features of newly installed 

technologies—such as their ability to interpret encrypted messages—may 

not be able to be fully utilized until all devices in the system have been 

replaced and the upgrade is complete. 

Securing Control Systems May Not Be Perceived as Economically Justifiable 

Experts and industry representatives have indicated that organizations 

may be reluctant to spend more money to secure control systems. 

Hardening the security of control systems would require industries to 

expend more resources, including acquiring more personnel, providing 
Page 20 GAO-04-628T 

training for personnel, and potentially prematurely replacing current 

systems, which typically have a lifespan of about 20 years. 

Several vendors suggested that since there have been no reports of 

significant disruptions caused by cyber attacks on U.S. control systems, 

industry representatives believe the threat of such an attack is low. While 

incidents have occurred, to date there is no formalized process for 

collecting and analyzing information about control systems incidents, thus 

further contributing to the skepticism of control systems vendors. We have 

previously recommended that the government work with the private 

sector to improve the quality and quantity of information being shared 

among industries and government about attacks on the nation’s critical 

infrastructures.14 

Until industry users of control systems have a business case to justify why 

additional security is needed, there may be little market incentive for the 

private sector to develop and implement more secure control systems. We 

have previously reported that consideration of further federal government 

efforts is needed to provide appropriate incentives for nonfederal entities 

to enhance their efforts to implement CIP—including protection of control 

systems. Without appropriate consideration of public policy tools, such as 

regulation, grants, and tax incentives, private-sector participation in 

sector-related CIP efforts may not reach its full potential.15

Organizational Priorities Conflict 

Finally, several experts and industry representatives indicated that the 

responsibility for securing control systems typically includes two separate 

groups: (1) IT security personnel and (2) control system engineers and 

operators. IT security personnel tend to focus on securing enterprise 

systems, while control system engineers and operators tend to be more 

concerned with the reliable performance of their control systems. These 

experts indicate that, as a result, those two groups do not always fully 

understand each other’s requirements and so may not effectively 

collaborate to implement secure control systems. 

 

14U.S. General Accounting Office, Critical Infrastructure Protection: Challenges for 

Selected Agencies and Industry Sectors, GAO-03-233 (Washington, D.C.: Feb. 28, 2003). 

15U.S. General Accounting Office, Homeland Security: Information Sharing

Responsibilities, Challenges, and Key Management Issues, GAO-03-1165T (Washington, 

D.C.: Sept. 17, 2003). 
Page 21 GAO-04-628T 

These conflicting priorities may perpetuate a lack of awareness of IT 

security strategies that could be deployed to mitigate the vulnerabilities of 

control systems without affecting their performance. Although research 

and development will be necessary to develop technologies to secure 

individual control system devices, existing IT security technologies and 

approaches could be implemented as part of a secure enterprise 

architecture to protect the perimeters of, and access to, control system 

networks. Existing IT security technologies include firewalls, intrusiondetection systems, encryption, authentication, and authorization. 

Approaches to IT security include segmenting control system networks 

and testing continuity plans to ensure safe and continued operation. 

To reduce the vulnerabilities of its control system, officials from one 

company formed a team composed of IT staff, process control engineers, 

and manufacturing employees. This team worked collaboratively to 

research vulnerabilities and to test fixes and workarounds. 

Efforts to Strengthen the Cybersecurity of Control Systems Under 

Way, but Lack Adequate Coordination 

Government, academia, and private industry have independently initiated 

multiple efforts and programs focused on some of the key areas that 

should be addressed to strengthen the cybersecurity of control systems. 

Our March 2004 report includes a detailed discussion of many initiatives. 

The key areas—and illustrative examples of ongoing efforts in these 

areas—include the following: 

• Research and development of new security technologies to protect 

control systems. Both federal and nonfederal entities have initiated 

efforts to develop encryption methods for securing communications on 

control system networks and field devices. Moreover, DOE is planning to 

establish a National SCADA Test Bed to test control system vulnerabilities. 

However, funding constraints have delayed the implementation of the 

initial phases of these plans. 

• Development of requirements and standards for control system 

security. Several entities are working to develop standards that increase 

the security of control systems. The North American Electric Reliability 

Council (NERC) is preparing to draft a standard that will include security 

requirements for control systems. In addition, the Process Controls 

Security Requirements Forum (PCSRF), established by NIST and NSA, is 

working to define a common set of information security requirements for 
Page 22 GAO-04-628T 

control systems. However, according to NIST officials, reductions to fiscal 

year 2004 appropriations will delay these efforts.

• Increased awareness of security and sharing of information about 

the implementation of more secure architectures and existing 

security technologies. To promote awareness of control system 

vulnerabilities, DOE has created security programs, trained teams to 

conduct security reviews, and developed cybersecurity courses. The 

Instrumentation Systems and Automation Society has reported on the 

known state of the art of cybersecurity technologies as they are applied to 

the control systems environment, to clearly define what technologies can 

currently be deployed. 

• Implementation of effective security management programs, 

including policies and guidance that consider control system 

security. Both federal and nonfederal entities have developed guidance to 

mitigate the security vulnerabilities of control systems. DOE’s 21 Steps to 

Improve Cyber Security of SCADA Networks provides guidance for 

improving the security of control systems and establishing underlying 

management processes and policies to help organizations improve the 

security of control system networks. 

In previous reports, we have recommended the development of a 

comprehensive and coordinated national plan to facilitate the federal 

government’s CIP efforts. This plan should clearly delineate the roles and 

responsibilities of federal and nonfederal CIP entities, define interim 

objectives and milestones, set time frames for achieving objectives, and 

establish performance measures. 

The President in his homeland security strategies and Congress in enacting 

the Homeland Security Act designated DHS as responsible for developing 

a comprehensive national infrastructure plan. The plan is expected to 

inform DHS on budgeting and planning for CIP activities and on how to 

use policy instruments to coordinate among government and private 

entities to raise the security of our national infrastructures to appropriate 

levels. According to Homeland Security Presidential Directive 7 (HSPD 7), 

issued December 17, 2003, DHS is to develop this formalized plan by 

December 2004. 

In February 2003, the President’s National Strategy to Secure Cyberspace

established a role for DHS to coordinate with other government agencies 

and the private sector to improve the cybersecurity of control systems. 

DHS’s assigned role includes: 
Page 23 GAO-04-628T 

• ensuring that there is broad awareness of the vulnerabilities in control 

systems and the consequences of exploiting these vulnerabilities, 

• developing best practices and new technologies to strengthen the security 

of control systems, and 

• identifying the nation’s most critical control system sites and developing a 

prioritized plan for ensuring cyber security at those sites. 

In addition, the President’s strategy recommends that DHS work with the 

private sector to promote voluntary standards efforts and the creation of 

security policy for control systems. 

DHS recently began to focus on the range of activities that are under way 

among the numerous entities that are working to address these areas. In 

October 2003, DHS’s Science and Technology Directorate initiated a study 

to determine the current state of security of control systems. In December 

2003, DHS established the Control Systems Section within the Protective 

Security Division of its Information Analysis and Infrastructure Protection 

(IAIP) Directorate. The objectives of this section are to identify computercontrolled systems that are vital to infrastructure functions, evaluate the 

potential threats to these systems, and develop strategies that mitigate the 

consequences of attacks. In addition, IAIP’s National Cyber Security 

Division (NCSD) is planning to develop a methodology for conducting 

cyber assessments across all critical infrastructures, including control 

systems. The objectives of this effort include defining specific goals for the 

assessments and, based on their results, developing sector-specific 

recommendations to mitigate vulnerabilities. NCSD also plans to examine 

processes, technology, and available policy, procedures, and guidance. 

Because these efforts have only recently been initiated, DHS 

acknowledges that it has not yet developed a strategy for implementing 

the functions mentioned above. 

As I previously mentioned, many government and nongovernment entities 

are spearheading various initiatives to address the challenge of 

implementing cybersecurity for the vital systems that operate our nation’s 

critical infrastructures. While some coordination is occurring, both federal 

and nonfederal control systems experts have expressed their concern that 

these efforts are not being adequately coordinated among government 

agencies, the private sector, and standards-setting bodies. DHS’s 

coordination of these efforts could accelerate the development and 

implementation of more secure systems to manage our critical 

infrastructures. In contrast, insufficient coordination could contribute to 
Page 24 GAO-04-628T 

• delays in the general acceptance of security requirements and the 

adoption of successful practices for control systems, 

• failure to address gaps in the research and development of technologies to 

better secure control systems, 

• impediments to standards-creating efforts across industries that could lead 

to less expensive technological solutions, and 

• reduced opportunities for efficiency that could be gained by leveraging 

ongoing work. 

In summary, it is clear that the systems that monitor and control the 

sensitive processes and physical functions of the nation’s critical 

infrastructures are at increasing risk from threats of cyber attacks. 

Securing these systems poses significant challenges. Numerous federal 

agencies, critical infrastructure sectors, and standards-creating bodies are 

leading various initiatives to address these challenges. DHS’s 

implementation of our recommendation—with which the department 

concurred—to develop and implement a strategy for better coordinating 

the cybersecurity of our critical infrastructures’ control systems among 

government and private sector entities can accelerate progress in securing 

these critical systems. Additionally, implementing existing IT technologies 

and security approaches can strengthen the security of control systems. 

These approaches include establishing an effective security management 

program, building successive layers of defense mechanisms at strategic 

access points to the control system network, and developing and testing 

continuity plans to ensure safe operation in the event of a power outage or 

cyber attack. 

Mr. Chairman, this concludes my statement. I would be pleased to answer 

any questions that you or other members of the Subcommittee may have at 

this time. 

If you should have any questions about this statement, please contact me 

at (202) 512-3317 or Elizabeth Johnston, Assistant Director, at (202) 512-

6345. We can also be reached by e-mail at daceyr@gao.gov and 

johnstone@gao.gov, respectively. 

Other individuals who made key contributors to this testimony include 

Shannin Addison, Joanne Fiorino, Alison Jacobs, Anjalique Lawrence, and 

Tracy Pierson.
Page 25 GAO-04-628T (310526) 
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