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Ethical hacking
by C. C. Palmer
The explosive growth of the Internet has brought
many good things: electronic commerce, easy
access to vast stores of reference material,
collaborative computing, e-mail, and new
avenues for advertising and information
distribution, to name a few. As with most
technological advances, there is also a dark side:
criminal hackers. Governments, companies, and
private citizens around the world are anxious to
be a part of this revolution, but they are afraid
that some hacker will break into their Web server
and replace their logo with pornography, read
their e-mail, steal their credit card number from
an on-line shopping site, or implant software that
will secretly transmit their organization’s secrets
to the open Internet. With these concerns and
others, the ethical hacker can help. This paper
describes ethical hackers: their skills, their
attitudes, and how they go about helping their
customers find and plug up security holes. The
ethical hacking process is explained, along with
many of the problems that the Global Security
Analysis Lab has seen during its early years of
ethical hacking for IBM clients.
T
he term “hacker” has a dual usage in the com-puter industry today. Originally, the term was
defined as:
HACKERnoun1. A person who enjoys learning the
details of computer systems and how to stretch
their capabilities—as opposed to most users of
computers, who prefer to learn only the minimum
amount necessary. 2. One who programs enthu-siastically or who enjoys programming rather than
just theorizing about programming.
1
This complimentary description was often extended
to the verb form “hacking,” which was used to de-scribe the rapid crafting of a new program or the
making of changes to existing, usually complicated
software.
As computers became increasingly available at uni-versities, user communities began to extend beyond
researchers in engineering or computer science to
other individuals who viewed the computer as a cu-riously flexible tool. Whether they programmed the
computers to play games, draw pictures, or to help
them with the more mundane aspects of their daily
work, once computers were available for use, there
was never a lack of individuals wanting to use them.
Because of this increasing popularity of computers
and their continued high cost, access to them was
usually restricted. When refused access to the com-puters, some users would challenge the access con-trols that had been put in place. They would steal
passwords or account numbers by looking over some-one’s shoulder, explore the system for bugs that
might get them past the rules, or even take control
of the whole system. They would do these things in
order to be able to run the programs of their choice,
or just to change the limitations under which their
programs were running.
Initially these computer intrusions were fairly benign,
with the most damage being the theft of computer
time. Other times, these recreations would take the
rCopyright 2001 by International Business Machines Corpora-tion. Copying in printed form for private use is permitted with-out payment of royalty provided that (1) each reproduction is done
without alteration and (2) the Journalreference and IBM copy-right notice are included on the first page. The title and abstract,
but no other portions, of this paper may be copied or distributed
royalty free without further permission by computer-based and
other information-service systems. Permission torepublish any
other portion of this paper must be obtained from the Editor.
IBM SYSTEMS JOURNAL, VOL 40, NO 3, 2001 0018-8670/01/$5.00 © 2001 IBM PALMER
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form of practical jokes. However, these intrusions did
not stay benign for long. Occasionally the less talented,
or less careful, intruders would accidentally bring down
a system or damage its files, and the system adminis-trators would have to restart it or make repairs. Other
times, when these intruders were again denied ac-cess once their activities were discovered, they would
react with purposefully destructive actions. When the
number of these destructive computer intrusions be-came noticeable, due to the visibility of the system
or the extent of the damage inflicted, it became
“news” and the news media picked up on the story.
Instead of using the more accurate term of “com-puter criminal,” the media began using the term
“hacker” to describe individuals who break into com-puters for fun, revenge, or profit. Since calling some-one a “hacker” was originally meant as a compliment,
computer security professionals prefer to use the
term “cracker” or “intruder” for those hackers who
turn to the dark side of hacking. For clarity, we will
use the explicit terms “ethical hacker” and “crim-inal hacker” for the rest of this paper.
What is ethical hacking?
With the growth of the Internet, computer security
has become a major concern for businesses and gov-ernments. They want to be able to take advantage
of the Internet for electronic commerce, advertis-ing, information distribution and access, and other
pursuits, but they are worried about the possibility
of being “hacked.” At the same time, the potential
customers of these services are worried about main-taining control of personal information that varies
from credit card numbers to social security numbers
and home addresses.
2
In their search for a way to approach the problem,
organizations came to realize that one of the best
ways to evaluate the intruder threat to their inter-ests would be to have independent computer secu-rity professionals attempt to break into their com-puter systems. This scheme is similar to having
independent auditors come into an organization to
verify its bookkeeping records. In the case of com-puter security, these “tiger teams” or “ethical hack-ers”
3
would employ the same tools and techniques
as the intruders, but they would neither damage the
target systems nor steal information. Instead, they
would evaluate the target systems’ security and re-port back to the owners with the vulnerabilities they
found and instructions for how to remedy them.
This method of evaluating the security of a system
has been in use from the early days of computers.
In one early ethical hack, the United States Air Force
conducted a “security evaluation” of the Multics op-erating systems for “potential use as a two-level
(secret/top secret) system.”
4
Their evaluation found
that while Multics was “significantly better than other
conventional systems,” it also had “... vulnerabil-ities in hardware security, software security, and pro-cedural security” that could be uncovered with “a
relatively low level of effort.” The authors performed
their tests under a guideline of realism, so that their
results would accurately represent the kinds of ac-cess that an intruder could potentially achieve. They
performed tests that were simple information-gath-ering exercises, as well as other tests that were out-right attacks upon the system that might damage its
integrity. Clearly, their audience wanted to know
both results. There are several other now unclassi-fied reports that describe ethical hacking activities
within the U.S. military.
5–7
With the growth of computer networking, and of the
Internet in particular, computer and network vul-nerability studies began to appear outside of the mil-itary establishment. Most notable of these was the
work by Farmer and Venema,
8
which was originally
posted to Usenet
9
in December of 1993. They dis-cussed publicly, perhaps for the first time,
10
this idea
of using the techniques of the hacker to assess the
security of a system. With the goal of raising the over-all level of security on the Internet and intranets, they
proceeded to describe how they were able to gather
enough information about their targets to have been
able to compromise security if they had chosen to
do so. They provided several specific examples of
how this information could be gathered and exploited
to gain control of the target, and how such an attack
could be prevented.
Farmer and Venema elected to share their report
freely on the Internet in order that everyone could
read and learn from it. However, they realized that
the testing at which they had become so adept might
be too complex, time-consuming, or just too boring
for the typical system administrator to perform on
a regular basis. For this reason, they gathered up all
the tools that they had used during their work, pack-aged them in a single, easy-to-use application, and
gave it away to anyone who chose to download it.
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Their program, called Security Analysis Tool for Au-diting Networks, or SATAN, was met with a great
amount of media attention around the world. Most
of this early attention was negative, because the tool’s
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capabilities were misunderstood. The tool was not
an automated hacker program that would bore into
systems and steal their secrets. Rather, the tool per-formed an audit that both identified the vulnerabil-ities of a system and provided advice on how to elim-inate them. Just as banks have regular audits of their
accounts and procedures, computer systems also
need regular checking. TheSATAN tool provided that
auditing capability, but it went one step further: it
also advised the user on how to correct the prob-lems it discovered. The tool did not tell the user how
the vulnerability might be exploited, because there
would be no useful point in doing so.
Who are ethical hackers?
These early efforts provide good examples of eth-ical hackers. Successful ethical hackers possess a va-riety of skills. First and foremost, they must be com-pletely trustworthy. While testing the security of a
client’s systems, the ethical hacker may discover in-formation about the client that should remain se-cret. In many cases, this information, if publicized,
could lead to real intruders breaking into the sys-tems, possibly leading to financial losses. During an
evaluation, the ethical hacker often holds the “keys
to the company,” and therefore must be trusted to
exercise tight control over any information about a
target that could be misused. The sensitivity of the
information gathered during an evaluation requires
that strong measures be taken to ensure the security
of the systems being employed by the ethical hack-ers themselves: limited-access labs with physical se-curity protection and full ceiling-to-floor walls, mul-tiple secure Internet connections, a safe to hold paper
documentation from clients, strong cryptography to
protect electronic results, and isolated networks for
testing.
Ethical hackers typically have very strong program-ming and computer networking skills and have been
in the computer and networking business for several
years. They are also adept at installing and main-taining systems that use the more popular operating
systems (e.g., UNIX** or WindowsNT**) used on tar-get systems. These base skills are augmented with
detailed knowledge of the hardware and software
provided by the more popular computer and net-working hardware vendors. It should be noted that
an additional specialization in security is not always
necessary, as strong skills in the other areas imply
a very good understanding of how the security on
various systems is maintained. These systems man-agement skills are necessary for the actual vulner-ability testing, but are equally important when pre-paring the report for the client after the test.
Finally, good candidates for ethical hacking have
more drive and patience than most people. Unlike
the way someone breaks into a computer in the mov-ies, the work that ethical hackers do demands a lot
of time and persistence. This is a critical trait, since
criminal hackers are known to be extremely patient
and willing to monitor systems for days or weeks
while waiting for an opportunity. A typical evalua-tion may require several days of tedious work that
is difficult to automate. Some portions of the eval-uations must be done outside of normal working
hours to avoid interfering with production at “live”
targets or to simulate the timing of a real attack.
When they encounter a system with which they are
unfamiliar, ethical hackers will spend the time to
learn about the system and try to find its weaknesses.
Finally, keeping up with the ever-changing world of
computer and network security requires continuous
education and review.
One might observe that the skills we have described
could just as easily belong to a criminal hacker as
to an ethical hacker. Just as in sports or warfare,
knowledge of the skills and techniques of your op-ponent is vital to your success. In the computer se-curity realm, the ethical hacker’s task is the harder
one. With traditional crime anyone can become a
shoplifter, graffiti artist, or a mugger. Their poten-tial targets are usually easy to identify and tend to
be localized. The local law enforcement agents must
know how the criminals ply their trade and how to
stop them. On the Internet anyone can download
criminal hacker tools and use them to attempt to
break into computers anywhere in the world. Eth-ical hackers have to know the techniques of the crim-inal hackers, how their activities might be detected,
and how to stop them.
Just as in sports or warfare,
knowledge of the skills
and techniques of your opponent
is vital to your success.
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Given these qualifications, how does one go about
finding such individuals? The best ethical hacker can-didates will have successfully published research pa-pers or released popular open-source security soft-ware.
12
The computer security community is strongly
self-policing, given the importance of its work. Most
ethical hackers, and many of the better computer and
network security experts, did not set out to focus on
these issues. Most of them were computer users from
various disciplines, such as astronomy and physics,
mathematics, computer science, philosophy, or lib-eral arts, who took it personally when someone dis-rupted their work with a hack.
One rule that IBM’s ethical hacking effort had from
the very beginning was that we would not hire ex-hackers. While some will argue that only a “real
hacker” would have the skill to actually do the work,
we feel that the requirement for absolute trust elim-inated such candidates. We likened the decision to
that of hiring a fire marshal for a school district: while
a gifted ex-arsonist might indeed know everything
about setting and putting out fires, would the par-ents of the students really feel comfortable with such
a choice? This decision was further justified when
the service was initially offered: the customers them-selves asked that such a restriction be observed. Since
IBM’s ethical hacking group was formed, there have
been numerous ex-hackers who have become secu-rity consultants and spokespersons for the news me-dia. While they may very well have turned away from
the “dark side,” there will always be a doubt.
What do ethical hackers do?
An ethical hacker’s evaluation of a system’s security
seeks answers to three basic questions:
c
What can an intruder see on the target systems?
c
What can an intruder do with that information?
c
Does anyone at the target notice the intruder’s at-tempts or successes?
While the first and second of these are clearly im-portant, the third is even more important: If the own-ers or operators of the target systems do not notice
when someone is trying to break in, the intruders
can, and will, spend weeks or months trying and will
usually eventually succeed.
When the client requests an evaluation, there is quite
a bit of discussion and paperwork that must be done
up front. The discussion begins with the client’s an-swers to questions similar to those posed by Gar-finkel and Spafford:
13
1. What are you trying to protect?
2. What are you trying to protect against?
3. How much time, effort, and money are you will-ing to expend to obtain adequate protection?
A surprising number of clients have difficulty pre-cisely answering the first question: a medical center
might say “our patient information,” an engineer-ing firm might answer “our new product designs,”
and a Web retailer might answer “our customer da-tabase.”
All of these answers fall short, since they only de-scribe targets in a general way. The client usually has
to be guided to succinctly describe all of the critical
information assets for which loss could adversely af-fect the organization or its clients. These assets
should also include secondary information sources,
such as employee names and addresses (which are pri-vacy and safety risks), computer and network informa-tion (which could provide assistance to an intruder),
and other organizations with which this organization
collaborates (which provide alternate paths into the tar-get systems through a possibly less secure partner’s
system).
A complete answer to (2) specifies more than just
the loss of the things listed in answer to (1). There
are also the issues of system availability, wherein a
denial-of-service attack could cost the client actual
revenue and customer loss because systems were un-available. The world became quite familiar with de-nial-of-service attacks in February of 2000 when at-tacks were launched against eBay**, Yahoo!**,
E*TRADE**, CNN**, and other popular Web sites.
During the attacks, customers were unable to reach
these Web sites, resulting in loss of revenue and
“mind share.” The answers to (1) should contain
more than just a list of information assets on the or-ganization’s computer. The level of damage to an
organization’s good image resulting from a success-ful criminal hack can range from merely embarrass-ing to a serious threat to revenue. As an example of
a hack affecting an organization’s image, on Janu-ary 17, 2000, a U.S. Library of Congress Web site
was attacked. The original initial screen is shown in
Figure 1, whereas the hacked screen is shown in Fig-ure 2. As is often done, the criminal hacker left his
or her nickname, or handle, near the top of the page
in order to guarantee credit for the break-in.
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Some clients are under the mistaken impression that
their Web site would not be a target. They cite nu-merous reasons, such as “it has nothing interesting
on it” or “hackers have never heard of my compa-ny.” What these clients do not realize is that every
Web site is a target. The goal of many criminal hack-ers is simple: Do something spectacular and then
make sure that all of your pals know that you did it.
Another rebuttal is that many hackers simply do not
care who your company or organization is; they hack
your Web site because they can . For example, Web
administrators at UNICEF (United Nations Children’s
Fund) might very well have thought that no hacker
would attack them. However, in January of 1998,
their page was defaced as shown in Figures 3 and
4. Many other examples of hacked Web pages can
be found at archival sites around the Web.
14
Answers to the third question are complicated by the
fact that computer and network security costs come
in three forms. First there are the real monetary costs
incurred when obtaining security consulting, hiring
Figure 1  Library of Congress Web page before attack
IBM SYSTEMS JOURNAL, VOL 40, NO 3, 2001 PALMER
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personnel, and deploying hardware and software to
support security needs. Second, there is the cost of
usability: the more secure a system is, the more dif-ficult it can be to make it easy to use. The difficulty
can take the form of obscure password selection
rules, strict system configuration rules, and limited
remote access. Third, there is the cost of computer
and network performance. The more time a com-puter or network spends on security needs, such as
strong cryptography and detailed system activity log-ging, the less time it has to work on user problems.
Because of Moore’s Law,
15
this may be less of an issue
for mainframe, desktop, and laptop machines. Yet,
it still remains a concern for mobile computing.
The “get out of jail free card”
Once answers to these three questions have been de-termined, a security evaluation plan is drawn up that
identifies the systems to be tested, how they should
be tested, and any limitations on that testing. Com-monly referred to as a “get out of jail free card,” this
Figure 2  Hacked Library of Congress Web page
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is the contractual agreement between the client and
the ethical hackers, who typically write it together.
This agreement also protects the ethical hackers
against prosecution, since much of what they do dur-ing the course of an evaluation would be illegal in
most countries. The agreement provides a precise
description, usually in the form of network addresses
or modem telephone numbers, of the systems to be
evaluated. Precision on this point is of the utmost
importance, since a minor mistake could lead to the
evaluation of the wrong system at the client’s instal-lation or, in the worst case, the evaluation of some
other organization’s system.
Once the target systems are identified, the agreement
must describe how they should be tested. The best
evaluation is done under a “no-holds-barred” ap-proach. This means that the ethical hacker can try
Figure 3  UNICEF Web page before attack
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anything he or she can think of to attempt to gain
access to or disrupt the target system. While this is
the most realistic and useful, some clients balk at this
level of testing. Clients have several reasons for this,
the most common of which is that the target systems
are “in production” and interference with their op-eration could be damaging to the organization’s in-terests. However, it should be pointed out to such
clients that these very reasons are precisely why a
“no-holds-barred” approach should be employed. An
intruder will not be playing by the client’s rules. If
the systems are that important to the organization’s
well-being, they should be tested as thoroughly as
possible. In either case, the client should be made
fully aware of the risks inherent to ethical hacker eval-uations. These risks include alarmed staff and uninten-tional system crashes, degraded network or system per-formance, denial of service, and log-file size explosions.
Figure 4  Hacked UNICEF Web page
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Some clients insist that as soon as the ethical hack-ers gain access to their network or to one of their
systems, the evaluation should halt and the client be
notified. This sort of ruling should be discouraged,
because it prevents the client from learning all that
the ethical hackers might discover about their sys-tems. It can also lead to the client’s having a false
sense of security by thinking that the first security
hole found is the only one present. The evaluation
should be allowed to proceed, since where there is
one exposure there are probably others.
The timing of the evaluations may also be impor-tant to the client. The client may wish to avoid af-fecting systems and networks during regular work-ing hours. While this restriction is not recommended,
it reduces the accuracy of the evaluation only some-what, since most intruders do their work outside of
the local regular working hours. However, attacks
done during regular working hours may be more eas-ily hidden. Alerts from intrusion detection systems
may even be disabled or less carefully monitored dur-ing the day. Whatever timing is agreed to, the client
should provide contacts within the organization who
can respond to calls from the ethical hackers if a sys-tem or network appears to have been adversely af-fected by the evaluation or if an extremely danger-ous vulnerability is found that should be immediately
corrected.
It is common for potential clients to delay the eval-uation of their systems until only a few weeks or days
before the systems need to go on-line. Such last-minute evaluations are of little use, since implemen-tations of corrections for discovered security prob-lems might take more time than is available and may
introduce new system problems.
In order for the client to receive a valid evaluation,
the client must be cautioned to limit prior knowl-edge of the test as much as possible. Otherwise, the
ethical hackers might encounter the electronic equiv-alent of the client’s employees running ahead of
them, locking doors and windows. By limiting the
number of people at the target organization who
know of the impending evaluation, the likelihood
that the evaluation will reflect the organization’s ac-tual security posture is increased. A related issue that
the client must be prepared to address is the rela-tionship of the ethical hackers to the target organi-zation’s employees. Employees may view this “sur-prise inspection” as a threat to their jobs, so the
organization’s management team must be prepared
to take steps to reassure them.
The ethical hack itself
Once the contractual agreement is in place, the test-ing may begin as defined in the agreement. It should
be noted that the testing itself poses some risk to
the client, since a criminal hacker monitoring the
transmissions of the ethical hackers could learn the
same information. If the ethical hackers identify a
weakness in the client’s security, the criminal hacker
could potentially attempt to exploit that vulnerabil-ity. This is especially vexing since the activities of the
ethical hackers might mask those of the criminal
hackers. The best approach to this dilemma is to
maintain several addresses around the Internet from
which the ethical hacker’s transmissions will ema-nate, and to switch origin addresses often. Complete
logs of the tests performed by the ethical hackers
are always maintained, both for the final report and
in the event that something unusual occurs. In ex-treme cases, additional intrusion monitoring software
can be deployed at the target to ensure that all the
tests are coming from the ethical hacker’s machines.
However, this is difficult to do without tipping off
the client’s staff and may require the cooperation of
the client’s Internet service provider.
The line between criminal hacking and computer vi-rus writing is becoming increasingly blurred. When
requested by the client, the ethical hacker can per-form testing to determine the client’s vulnerability
to e-mail or Web-based virus vectors. However, it
is far better for the client to deploy strong antivirus
software, keep it up to date, and have a clear and
simple policy in place for the reporting of incidents.
IBM’s Immune System for Cyberspace
16,17
is another
approach that provides the additional capability of
recognizing new viruses and reporting them to a cen-tral lab that automatically analyzes the virus and pro-vides an immediate vaccine.
As dramatized in Figure 5, there are several kinds
of testing. Any combination of the following may be
called for:
c
Remote network . This test simulates the intruder
launching an attack across the Internet. The pri-mary defenses that must be defeated here are bor-der firewalls, filtering routers, and Web servers.
c
Remote dial-up network . This test simulates the in-truder launching an attack against the client’s mo-dem pools. The primary defenses that must be de-feated here are user authentication schemes. These
kinds of tests should be coordinated with the local
telephone company.
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c
Local network . This test simulates an employee or
other authorized person who has a legal connec-tion to the organization’s network. The primary
defenses that must be defeated here are intranet
firewalls, internal Web servers, server security mea-sures, and e-mail systems.
c
Stolen laptop computer. In this test, the laptop com-puter of a key employee, such as an upper-level
manager or strategist, is taken by the client with-out warning and given to the ethical hackers. They
examine the computer for passwords stored in di-al-up software, corporate information assets, per-sonnel information, and the like. Since many busy
users will store their passwords on their machine,
it is common for the ethical hackers to be able to
use this laptop computer to dial into the corpo-rate intranet with the owner’s full privileges.
c
Social engineering. This test evaluates the target or-ganization’s staff as to whether it would leak in-formation to someone. A typical example of this
would be an intruder calling the organization’s
computer help line and asking for the external tele-phone numbers of the modem pool. Defending
against this kind of attack is the hardest, because
people and personalities are involved. Most peo-ple are basically helpful, so it seems harmless to
tell someone who appears to be lost where the
computer room is located, or to let someone into
the building who “forgot” his or her badge. The
only defense against this is to raise security aware-ness.
c
Physical entry . This test acts out a physical pene-tration of the organization’s building. Special ar-rangements must be made for this, since security
guards or police could become involved if the eth-ical hackers fail to avoid detection. Once inside
the building, it is important that the tester not be
detected. One technique is for the tester to carry
a document with the target company’s logo on it.
Such a document could be found by digging
through trash cans before the ethical hack or by
casually picking up a document from a trash can
or desk once the tester is inside. The primary de-fenses here are a strong security policy, security
Figure 5  Different ways to attack computer security
OUTSIDE BAD GUY
STOL E N   L A P TOP S
D MZ
I N SIDE BAD GUY
INTRANET
E X TRANET
F IRE WA LL
W E B
INTERNET
S ERV I C E S
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guards, access controls and monitoring, and secu-rity awareness.
Each of these kinds of testing can be performed from
three perspectives: as a total outsider, a “semi-out-sider,” or a valid user.
A total outsider has very limited knowledge about
the target systems. The only information used is avail-able through public sources on the Internet. This test
represents the most commonly perceived threat. A
well-defended system should not allow this kind of
intruder to do anything.
A semi-outsider has limited access to one or more
of the organization’s computers or networks. This
tests scenarios such as a bank allowing its deposi-tors to use special software and a modem to access
information about their accounts. A well-defended
system should only allow this kind of intruder to ac-cess his or her own account information.
A valid user has valid access to at least some of the
organization’s computers and networks. This tests
whether or not insiders with some access can extend
that access beyond what has been prescribed. A well-defended system should allow an insider to access
only the areas and resources that the system admin-istrator has assigned to the insider.
The actual evaluation of the client’s systems proceeds
through several phases, as described previously by
Boulanger.
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The final report
The final report is a collection of all of the ethical
hacker’s discoveries made during the evaluation.
Vulnerabilities that were found to exist are explained
and avoidance procedures specified. If the ethical
hacker’s activities were noticed at all, the response
of the client’s staff is described and suggestions for
improvements are made. If social engineering test-ing exposed problems, advice is offered on how to
raise awareness. This is the main point of the whole
exercise: it does clients no good just to tell them that
they have problems. The report must include spe-cific advice on how to close the vulnerabilities and
keep them closed. The actual techniques employed
by the testers are never revealed. This is because the
person delivering the report can never be sure just
who will have access to that report once it is in the
client’s hands. For example, an employee might want
to try out some of the techniques for himself or her-self. He or she might choose to test the company’s
systems, possibly annoying system administrators or
even inadvertently hiding a real attack. The employee
might also choose to test the systems of another or-ganization, which is a felony in the United States
when done without permission.
The actual delivery of the report is also a sensitive
issue. If vulnerabilities were found, the report could
be extremely dangerous if it fell into the wrong hands.
A competitor might use it for corporate espionage,
a hacker might use it to break into the client’s com-puters, or a prankster might just post the report’s
contents on the Web as a joke. The final report is
typically delivered directly to an officer of the client
organization in hard-copy form. The ethical hack-ers would have an ongoing responsibility to ensure
the safety of any information they retain, so in most
cases all information related to the work is destroyed
at the end of the contract.
Once the ethical hack is done and the report deliv-ered, the client might ask “So, if I fix these things
I’ll have perfect security, right?” Unfortunately, this
is not the case. People operate the client’s comput-ers and networks, and people make mistakes. The
longer it has been since the testing was performed,
the less can be reliably said about the state of a cli-ent’s security. A portion of the final report includes
recommendations for steps the client should con-tinue to follow in order to reduce the impact of these
mistakes in the future.
Conclusions
The idea of testing the security of a system by trying
to break into it is not new. Whether an automobile
company is crash-testing cars, or an individual is test-ing his or her skill at martial arts by sparring with
a partner, evaluation by testing under attack from
a real adversary is widely accepted as prudent. It is,
however, not sufficient by itself. As Roger Schell ob-served nearly 30 years ago:
From a practical standpoint the security problem
will remain as long as manufacturers remain com-mitted to current system architectures, produced
without a firm requirement for security.As long
as there is support for ad hoc fixes and security pack-ages for these inadequate designs and as long as the
illusory results of penetration teams are accepted as
demonstrations of a computer system security, proper
security will not be a reality .
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Regular auditing, vigilant intrusion detection, good
system administration practice, and computer secu-rity awareness are all essential parts of an organi-zation’s security efforts. A single failure in any of
these areas could very well expose an organization
to cyber-vandalism, embarrassment, loss of revenue
or mind share, or worse. Any new technology has its
benefits and its risks. While ethical hackers can help
clients better understand their security needs, it is
up to the clients to keep their guards in place.
Acknowledgments
The author would like to thank several people: the
members of the Global Security Analysis Lab at IBM
Research for sharing their amazing expertise and
their ability to make just about anyone understand
more about security; Chip Coy and Nick Simicich
for their trailblazing work in defining IBM’s Security
Consulting Practice at the very beginning; and Paul
Karger for his encyclopedic knowledge of computer
security research and for his amazing ability to pro-duce copies of every notable paper on the subject
that was ever published.
**Trademark or registered trademark of the Open Group, Mi-crosoft Corporation, eBay Inc., Yahoo! Inc., E*TRADE Secu-rities, Inc., or Cable News Network LP, LLLP.
Cited references and notes
1. E. S. Raymond, The New Hacker’s Dictionary, MIT Press,
Cambridge, MA (1991).
2. S. Garfinkel, Database Nation , O’Reilly & Associates, Cam-bridge, MA (2000).
3. The first use of the term “ethical hackers” appears to have
been in an interview with John Patrick of IBM by Gary An-thens that appeared in a June 1995 issue of ComputerWorld.
4. P. A. Karger and R. R. Schell, Multics Security Evaluation:
Vulnerability Analysis , ESD-TR-74-193, Vol. II, Headquar-ters Electronic Systems Division, Hanscom Air Force Base,
MA (June 1974).
5. S. M. Goheen and R. S. Fiske, OS/360 Computer Security Pen-etration Exercise , WP-4467, The MITRE Corporation, Bed-ford, MA (October 16, 1972).
6. R. P. Abbott, J. S. Chen, J. E. Donnelly, W. L. Konigsford,
and S. T. Tokubo,Security Analysis and Enhancements of Com-puter Operating Systems, NBSIR 76-1041, National Bureau
of Standards, Washington, DC (April 1976).
7. W. M. Inglis, Security Problems in the WWMCCS GCOS Sys-tem , Joint Technical Support Activity Operating System Tech-nical Bulletin 730S-12, Defense Communications Agency
(August 2, 1973).
8. D. Farmer and W. Z. Venema, “Improving the Security of Your
Site by Breaking into It,” originally posted to Usenet (Decem-ber 1993); it has since been updated and is now available at
ftp://ftp.porcupine.org/pub/security/index.html#documents.
9. See http://www.faqs.org/usenet/.
10. Who can really determine who said something first on the
Internet?
11. See http://www.cs.ruu.nl/cert-uu/satan.html.
12. This strategy is based on the ideal of raising the security of
the whole Internet by giving security software away. Thus,
no one will have any excuse not to take action to improve
security.
13. S. Garfinkel and E. Spafford, Practical Unix Security, First Edi-tion, O’Reilly & Associates, Cambridge, MA (1996).
14. For a collection of previously hacked Web sites, see http://
www.2600.com/hacked_pages/ or http://defaced.alldes.de. Be
forewarned, however, that some of the hacked pages may con-tain pornographic images.
15. In 1965, Intel cofounder Gordon Moore was preparing a
speech and made a memorable observation. When he started
to graph data about the growth in memory chip performance,
he realized there was a striking trend. Each new chip con-tained roughly twice as much capacity as its predecessor, and
each chip was released within 18 –24 months of the previous
chip. In subsequent years, the pace slowed down a bit, but
data density has doubled approximately every 18 months, and
this is the current definition of Moore’s Law.
16. J. O. Kephart, G. B. Sorkin, D. M. Chess, and S. R. White,
“Fighting Computer Viruses,” Scientific American277, No.
5, 88 –93 (November 1997).
17. See http://www.research.ibm.com/antivirus/SciPapers.htm for
additional antivirus research papers.
18. A. Boulanger, “Catapults and Grappling Hooks: The Tools
and Techniques of Information Warfare,” IBM Systems Jour-nal 37, No. 1, 106 –114 (1998).
19. R. R. Schell, P. J. Downey, and G. J. Popek, Preliminary Notes
on the Design of Secure Military Computer Systems, MCI-73-1,
ESD/AFSC, Hanscom Air Force Base, Bedford, MA (Jan-uary 1973).
Accepted for publication April 13, 2001.
Charles C. Palmer IBM Research Division, Thomas J. Watson
Research Center, P.O. Box 218, Yorktown Heights, New York 10598
(electronic mail: ccpalmer@us.ibm.com). Dr. Palmer manages the
Network Security and Cryptography department at the IBM Tho-mas J. Watson Research Center. His teams work in the areas of
cryptography research, Internet security technologies, Java
TM
se-curity, privacy, and the Global Security Analysis Lab (GSAL),
which he cofounded in 1995. As part of the GSAL, Dr. Palmer
worked with IBM Global Services to start IBM’s ethical hacking
practice. He frequently speaks on the topics of computer and net-work security at conferences around the world. He was also an
adjunct professor of computer science at Polytechnic University,
Hawthorne, New York, from 1993 to 1997. He holds four patents
and has several publications from his work at IBM and Polytech-nic.
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