Gary S. Morris
GSM Associates
Suite 202
7338 Lee Highway
Falls Church, Virginia 22046
(703) 685-3021



                  Computer Security and the Law

I.  Introduction

     You are a computer administrator for a large manufacturing
company.  In the middle of a production run, all of the
mainframes on a crucial network grind to a halt.  Production is
delayed costing your company hundreds of thousands of dollars.
Upon investigating, you find that a virus was released into the
network through a specific account.  When you confront the owner
of the account, he claims he neither wrote nor released the
virus, but admits that he has distributed his password to
"friends" who need ready access to his data files.  Is he liable
for the loss suffered by your company? In whole, or in part? And
if in part, for how much?  These and related questions are the
subject of computer security law.  The answers may vary depending
on the state in which the crime was committed and the judge who
presides at the trial.  Computer security law is a new field, and
the legal establishment has yet to reach broad agreement on many
key issues. Even the meaning of such basic terms as "data" can be
the subject of contention.

     Advances in computer security law have been impeded by the
reluctance on the part of lawyers and judges to grapple with the
technical side of computer security issues [1].  This problem
could be mitigated by involving technical computer security
professionals in the development of computer security law and
public policy.  This article is meant to help bridge the gap
between the technical and legal computer security communities by 
explaining key technical ideas behind computer security for
lawyers and presenting some basic legal background for technical
professionals.

II.  The Technological Perspective

     A. The Objectives of Computer Security

     The principal objective of computer security is to protect
and assure the confidentiality, integrity, and availability of
automated information systems and the data they contain. Each of
these terms has a precise meaning which is grounded in basic
technical ideas about the flow of information in automated
information systems.  

     B.   Basic Concepts 

      There is a broad, top-level consensus regarding the meaning
of most technical computer security concepts.  This is partly
because of government involvement in proposing, coordinating, and
publishing the definitions of basic terms [2].  The meanings of
the terms used in government directives and regulations are
generally made to be consistent with past usage.  This is not to
say that there is no disagreement over definitions in the
technical community. Rather, the range of such disagreement is
much narrower than in the legal community.  For example, there is
presently no legal consensus on exactly what constitutes a
computer [3].

     The term used to establish the scope of computer security is
"automated information system," often abbreviated "AIS."  An AIS
is any assembly of electronic equipment, hardware, software, and
firmware configured to collect, create, communicate, disseminate,
process, store, and control data or information.  This includes
numerous items beyond the central processing unit and associated
random access memory, such as input/output devices (keyboards,
printers, etc.)

     Every AIS is used by subjects to act upon objects.  A
subject is any active entity that causes information to flow
among passive entities called objects.  For example, subject
could be a person typing commands which transfer information from
a keyboard (an object) to memory (another object), or a process
running on the central processing unit that is sending
information from a file (an object) to a printer (another
object).

     Confidentiality is roughly equivalent to privacy.  If a
subject circumvents confidentiality measures designed to prevent
its access to an object, the object is said to be "compromised." 
Confidentiality is the most advanced area of computer security
because the U.S. Department of Defense has invested heavily for
many years to find ways to maintain the confidentiality of
classified data in AIS [4].  This investment has produced the
Department of Defense Trusted Computer System Evaluation
Criteria [5], alternatively called the Orange Book after the
color of its cover.  The Orange Book is perhaps the single most
authoritative document about protecting the confidentiality of
data in classified AIS. 

     Integrity measures are meant to protect data from
unauthorized modification.  The integrity of an object can be
assessed by comparing its current state to its original or
intended state.  An object which has been modified by a subject
without proper authorization is said to be "corrupted." 
Technology for ensuring integrity has lagged behind that for
confidentiality [4].  This is because the integrity problem has
until recently been addressed by restricting access to AIS to
trustworthy subjects. Today, the integrity threat is no longer
tractable exclusively through access control.  The desire for
wide connectivity through networks and the increased use of
commercial-off-the-shelf software has limited the degree to which
 most AISs can trust its subjects.  Work in integrity has been
accelerating over the past few years, and will likely become as
important a priority as confidentiality in the future.

     Availability means having an AIS and its associated objects
accessible and functional when needed by its user community. 
Attacks against availability are called denial of service
attacks.  For example, a subject may release a virus which
absorbs so much processor time that the AIS becomes overloaded. 
This area is by far the least well developed of the three
security properties, largely for technical reasons involving the
formal verification of AIS designs [4].  Although such
verification is not likely to become a practical reality for many
years, techniques such as fault tolerance and software
reliability are used to mitigate the effects of denial of service
attacks.

     C.  Computer Security Requirements

     The three security properties of confidentiality, integrity,
and availability are achieved by labeling the subjects and
objects in an AIS and regulating the flow of information between
them according to a predetermined set of rules called a security
policy.  The security policy specifies which subject labels can
access which object labels.  For example, suppose you went
shopping and had to present your driver's license to pick up some
badges assigned to you at the entrance, each listing a brand
name.  The policy at this store is that you can only buy brand
names listed on one of your badges.  At the check-out line, the
cashier compares the brand name of each object you want to buy
with the names on your badges.  If there's a match, she rings it
up.  But if you choose a brand name which doesn't appear on one
of your badges, she puts it back on the shelf. You could be
sneaky and alter a badge, or pretend to be your neighbor who has
more badges than you, or find a clerk who will turn a blind eye. 
No doubt the store would employ a host of measures to prevent you
from cheating.  The same situation exists on secure computer
systems.  Security measures are employed to prevent illicit
tampering with labels, positively identify subjects, and provide
assurance that the security measures are doing the job correctly. 
A comprehensive list of minimal requirements to secure an AIS are
presented in the Orange Book [5]. 

III.  The Legal Perspective

     A.   Sources of Computer Law

          The three branches of government, legislative,
executive and judicial, produce quantities of computer law which
are inveresly proportional to the amount of coordination needed
for its enactment.  The legislative branch, consisting of the
Congress and fifty state legislatures, produce the smallest
amount of law which is worded in the most general terms.  For
example, the Congress may pass a bill mandating that sensitive
information in government computers must be protected.  The
 executive branch, consisting of the Executive Office of the
President and numerous agencies, issues regulations which
implement the bills passed by legislatures.  Thus, the Department
of Commerce may issue regulations which establish criteria for
determining when economic information is sensitive and describe
how it must be protected.  Finally, the judicial branch serves as
an avenue of appeal and decides the meaning of the laws and
regulations in specific cases.  After the decisions are issued
(and in some cases appealed) they are taken as the word of the
law in legally similar situations.  

     B. Current Views on Computer Crime

     Currently, there is no universal agreement in the legal
community on what constitutes a computer crime.  One reason is
the rapidly changing state of computer technology.  For example,
in 1979, the U.S. Department of Justice publication [6]
partitioned computer crime into three categories:  1) Computer
abuse,  "the broad range of international acts involving a
computer where one or more perpetrators made or could have made
gain and one or more victims suffered or could have suffered a
loss;"  2) Computer crime, "illegal computer abuse [that] implies
direct involvement of computers in committing a crime;" and
3) Computer-related crime,  "any illegal act for which a
knowledge of computer technology is essential for successful
prosecution."  These definitions have become blurred by the vast
proliferation of computers and computer related products over the
last decade.  For example, does altering an inventory bar code at
a store constitute computer abuse?  Should a person caught in
such an act be prosecuted under both theft and computer abuse
laws?  Clearly, advances in computer technology should be
mirrored by parallel changes in computer law. 

     Another attempt to describe the essential features of
computer crime has been made by Wolk and Luddy [1].  They claim
that the majority of crimes committed against or with the use of
a computer can be classified as follows:

     1) Sabotage: "Involves an attack against the entire
     [computer] system or against its subcomponents, and may be
     the product of foreign power involvement or penetration by a
     competitor..."
     2) Theft of services: "Using a computer at someone else's
     expense."
     3) Property crimes involving the "theft of property by and
     through the use of computers." [7]  

A good definition of computer crime should capture all acts which
are criminal and involve computers and only those acts. Assessing
the completeness of a definition seems problematic, but is
tractable using technical computer security concepts.  For
example, consider the following matrix:


                     Confidentiality    Integrity    Availability
 
Sabotage                                    X             X

Theft of Services                                         X

Property Crimes             X                             X


This shows that Wolk and Luddy's categorization is strong with
respect to availability and weaker in the areas of
confidentiality and integrity.  Indeed, upon closer examination
it becomes apparent that there are ways to violate
confidentiality and integrity which do not constitute sabotage,
theft of services, or property crimes.  For example, a Trojan
horse could append code to a word processor which sends copies of
a user's confidential text as messages to the perpetrator's
electronic mailbox. This isn't sabotage because no AIS
functionality was destroyed or even altered; theft of services
does not apply if the perpetrator is paying for his electronic
mail account; and unless the confidential text was copyrighted,
it is not a property crime. This analysis is significant because
it demonstrates that examining a legal concept from a technical
perspective can yield insights into its strengths and weaknesses
and even suggest avenues for improvement.

IV.  Conclusion

     The development of effective computer security law and
public policy cannot be accomplished without cooperation between
the technical and legal communities.  The inherently abstruse
nature of computer technology and the importance of the social
issues it generates demand the combined talents of both.  At
stake is not only a fair and just interpretation of the law as it
pertains to computers, but more basic issues involving the
protection of civil rights.  Technological developments have
challenged these rights in the past and have been met with laws
and public policies which have regulated their use.  For example,
the invention of the telegraph and telephone gave rise to privacy
laws pertaining to wire communications. We need to meet advances
in automated information technology with legislation that
preserves civil liberties and establishes legal boundaries for
protecting confidentiality, integrity, and assured service. Legal
and computer professionals have a vital role in meeting this
challenge together.

                          REFERENCES

[1]  Stuart R. Wolk and William J. Luddy Jr., "Legal Aspects of
Computer Use," Prentice Hall, 1986, pg. 129.

[2]  National Computer Security Center, "Glossary of Computer
Security Terms," 21 October 1988.

[3]  Thomas R. Mylott III, "Computer Law for the Computer
Professional," Prentice Hall, 1984, pg. 131.
 
[4]  Gasser, Morrie, "Building a Secure Computer System," Van
Nostrand, 1988.

[5]  Department of Defense, "Department of Defense Trusted
Computer System Evaluation Criteria," December 1985.

[6]  United States Department of Justice, "Computer Crime,
Criminal Justice Resource Manual," 1979. 

[7]  Wolk and Luddy, pg. 117.

