CSL - Computer Systems Laboratory Bulletin
                        March 1994

THREATS TO COMPUTER SYSTEMS:  AN OVERVIEW
Computer systems are vulnerable to many threats which can inflict
various types of damage resulting in significant losses.  Damage
can range from minor errors which sap database integrity to fires
which destroy entire computer centers.  Losses can stem from the
actions of supposedly trusted employees defrauding the system to
outside hackers roaming freely through the Internet.  The exact
amount of computer-related losses is unknowable; many losses are
never discovered and others are covered up to avoid unfavorable
publicity. 

This bulletin increases reader awareness of threats to computer
systems by giving a broad picture of the threat environment in
which systems are operated today.  An overview of many of today's
common threats will be useful to organizations studying their own
threat environments with a view toward developing solutions
specific to their organization.

This bulletin summarizes a chapter of the computer security
handbook being developed by CSL.  We have already published
bulletins summarizing other chapters on establishing a computer
security program, considering people issues in computer security,
and developing computer security policy.  Additional bulletins
will be issued as chapters are finalized.

Common Threats
A wide variety of threats face today's computer systems and the
information they process.  In order to control the risks of
operating an information system, managers and users must know the
vulnerabilities of the system and the threats which may exploit
them.  Knowledge of the threat environment allows the system
manager to implement the most cost-effective security measures. 
In some cases, managers may find it most cost-effective to simply
tolerate the expected losses.

The following threats and associated losses are based on their
prevalence and significance in the current computing environment
and their expected growth.  The list is not exhaustive; some
threats may combine elements from more than one area.  

Errors and Omissions
Users, data entry clerks, system operators, and programmers
frequently make unintentional errors which contribute to security
problems, directly and indirectly.  Sometimes the error is the
threat, such as a data entry error or a programming error that
crashes a system.  In other cases, errors create vulnerabilities. 
Errors can occur in all phases of the system life cycle.  

Programming and development errors, often called bugs, range in
severity from benign to catastrophic.  In the past decade,
software quality has improved measurably to reduce this threat,
yet software "horror stories" still abound.  Installation and
maintenance errors also cause security problems.  

Errors and omissions are important threats to data integrity. 
Errors are caused not only by data entry clerks processing
hundreds of transactions per day, but by all users who create and
edit data.  Many programs, especially those designed by users for
personal computers, lack quality control measures.  However, even
the most sophisticated programs cannot detect all types of input
errors or omissions.

The computer age saying "garbage in, gospel out" contains a large
measure of truth.  People often assume that the information they
receive from a computer system is more accurate than it really
is.  Many organizations address errors and omissions in their
computer security, software quality, and data quality programs.

Fraud and Theft
Information technology is increasingly used to commit fraud and
theft.  Computer systems are exploited in numerous ways, both by
automating traditional methods of fraud and by using new methods. 
For example, individuals may use a computer to skim small amounts
of money from a large number of financial accounts, thus
generating a significant sum for their own use.  Also, deposits
may be intentionally misdirected.  Financial systems are not the
only ones subject to fraud.  Systems which control access to any
resource are targets, such as time and attendance systems,
inventory systems, school grading systems, or long-distance
telephone systems.  

Fraud can be committed by insiders or outsiders.  The majority of
fraud uncovered on computer systems is perpetrated by insiders
who are authorized users of a system.  Since insiders have both
access to and familiarity with the victim computer system,
including what resources it controls and where the flaws are,
authorized system users are in a better position to commit
crimes.  An organization's former employees may also pose
threats, particularly if their access is not terminated promptly.

Disgruntled Employees
Disgruntled employees can create both mischief and sabotage on a
computer system.  Employees are the group most familiar with
their employer's computers and applications, including knowing
what actions might cause the most damage.  Organizational
downsizing in both public and private sectors has created a group
of individuals with organizational knowledge who may retain
potential system access.  System managers can limit this threat
by invalidating passwords and deleting system accounts in a
timely manner.  However, disgruntled current employees actually
cause more damage than former employees.

Common examples of computer-related employee sabotage include:

         -       Entering data incorrectly
         -       Changing data
         -       Deleting data
         -       Destroying data or programs with logic bombs
         -       "Crashing" systems
         -       Holding data hostage
         -       Destroying hardware or facilities

Physical and Infrastructure 
The loss of supporting infrastructure includes power failures
(including outages, spikes and brownouts), loss of
communications, water outages and leaks, sewer problems, lack of
transportation services, fire, flood, civil unrest, strikes, and
so forth.  These losses include dramatic events such as the
explosion at the World Trade Center and the Chicago tunnel flood
as well as more common events such as a broken water pipe. 
System owners must realize that more loss is associated with
fires and floods than with viruses and other more widely
publicized threats.    

A loss of infrastructure often results in system downtime,
sometimes in unexpected ways.  For example, employees may not be
able to get to work during a winter storm, although the computer
system may be functional.  

Malicious Hackers
Hackers, sometimes called crackers, are a real and present danger
to most organizational computer systems linked by networks.  From
outside the organization, sometimes from another continent,
hackers break into computer systems and compromise the privacy
and integrity of data before the unauthorized access is even
detected.  Although insiders cause more damage than hackers, the
hacker problem remains serious and widespread.

The effect of hacker activity on the public switched telephone
network has been studied in depth.  Studies by the National
Research Council and the National Security Telecommunications
Advisory Committee show that hacker activity is not limited to
toll fraud.  It also includes the ability to break into
telecommunications systems (such as switches) resulting in the
degradation or disruption of system availability.  While unable
to reach a conclusion about the degree of threat or risk, these
studies underscore the ability of hackers to cause serious
damage.

The hacker threat often receives more attention than more common
and dangerous threats.  The U.S. Department of Justice's Computer
Crime Unit suggests three reasons.  First, the hacker threat is a
more recently encountered threat.  Organizations have always had
to worry about the actions of their own employees and could use
disciplinary measures to reduce that threat.  However, these
controls are ineffective against outsiders who are not subject to
the rules and regulations of the employer.  

Secondly, organizations do not know the purposes of a hacker;
some hackers only browse, some steal, some damage.  This
inability to identify purposes can suggest that hacker attacks
have no limitations.  Finally, hacker attacks make people feel
vulnerable because the perpetrators are unknown.  

Industrial Espionage
Industrial espionage involves collecting proprietary data from
private corporations or government agencies for the benefit of
another company or organization.  Industrial espionage can be
perpetrated either by companies seeking to improve their
competitive advantage or by governments seeking to aid their
domestic industries.  Foreign industrial espionage carried out by
a government is known as economic espionage.  

Industrial espionage is on the rise.  The most damaging types of
stolen information include manufacturing and product development
information.  Other types of information stolen include sales and
cost data, client lists, and research and planning information.

Within the area of economic espionage, the Central Intelligence
Agency states that the main objective is obtaining information
related to technology, but that information on U.S. government
policy deliberations concerning foreign affairs and information
on commodities, interest rates, and other economic factors is
also a target.  The Federal Bureau of Investigation concurs that
technology-related information is the main target, but also cites
corporate proprietary information such as negotiating positions
and other contracting data as a target.

Malicious Code
Malicious code refers to viruses, worms, Trojan horses, logic
bombs, and other "uninvited" software.  Malicious code is
sometimes mistakenly associated only with personal computers, but
can also attack more sophisticated systems.  However, actual
costs attributed to the presence of malicious code have resulted
primarily from system outages and staff time involved in
repairing the systems.  Nonetheless, these costs can be
significant.  

Malicious Software: A Few Key Terms

Virus:  A code segment which replicates by attaching copies of
itself to existing executables.  The new copy of the virus is
executed when a user executes the new host program.  The virus
may include an additional "payload" that triggers when specific
conditions are met.  For example, some viruses display a text
string on a particular date.  There are many types of viruses
including variants, overwriting, resident, stealth, and
polymorphic. 

Trojan Horse:  A program that performs a desired task, but also
includes unexpected (and undesirable) functions.  Consider as an
example an editing program for a multi-user system.  This program
could be modified to randomly delete one of the users' files each
time they perform a useful function (editing) but the deletions
are unexpected and definitely undesired!

Worm:  A self-replicating program which is self-contained and
does not require a host program.  The program creates a copy of
itself and causes it to execute; no user intervention is
required.  Worms commonly utilize network services to propagate
to other host systems.  
The number of known viruses is increasing, and the rate of virus
incidents is growing moderately.  Most organizations use anti-
virus software and other protective measures to limit the risk of
virus infection.

Foreign Government Espionage
In some instances, threats posed by foreign government
intelligence services may be present.  In addition to possible
economic espionage, foreign intelligence services may target
unclassified systems to further their intelligence missions.  

Threats to Personal Privacy
The accumulation of vast amounts of electronic information about
individuals by the government, credit bureaus, and private
companies combined with the ability of computers to monitor,
process, aggregate, and record information about individuals have
created a very real threat to individual privacy.  The
possibility that all of this information and technology could be
linked together has loomed as a specter of the modern information
age.  This phenomenon is known as "big brother."  

The threat to personal privacy arises from many sources.  Several
cases have been reported involving the sale of personal
information by federal and state employees to private
investigators or other "information brokers."  One such case was
uncovered in 1992 when the Justice Department announced the
arrest of over two dozen individuals engaged in buying and
selling information from Social Security Administration (SSA)
computer files.  In the course of the investigation, auditors
learned that SSA employees had unrestricted access to over 130
million employment records.

Just recently, an investigation found that five percent of the
employees in one region of the Internal Revenue Service had
browsed through tax records of friends, relatives, and
celebrities.  Some employees used the information to create
fraudulent tax refunds, but many acted simply out of curiosity.   

As more of these cases come to light, many individuals express
increased concern about threats to their personal privacy.  Over
the years, Congress has enacted legislation, such as the Privacy
Act of 1974 and the Computer Matching and Privacy Protection Act
of 1988, which defines the boundaries of the legitimate uses of
personal information collected by the government.    

While the magnitude and cost to society of the personal privacy
threat are difficult to gauge, information technology has become
powerful enough to warrant fears of both government and corporate
"big brothers."  Increased awareness of the problem is needed. 

Conclusion
Today's computer systems, linked by national and global networks,
face a variety of threats which can result in significant
financial and information losses.  Threats vary considerably,
from threats to data integrity resulting from unintentional
errors and omissions to threats to system availability from
malicious hackers attempting to crash a system.  An understanding
of the types of threats in today's computing environment can
assist a security manager in selecting appropriate cost-effective
controls to protect valuable information resources.