The term “hacker” has a dual usage in the computer industry today. Originally, the term was defined as:
“ 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. One who programs enthusiastically or who enjoys programming rather than just theorizing about programming”.
This complimentary description was often extended to the verb form “hacking,” which was used to describe the rapid crafting of a new program or the making of changes to existing, usually complicated software.
Because of the increasing popularity of computers and their continued high cost, access to them was usually restricted. When refused access to the computers, some users would challenge the access controls that had been put in place. They would steal passwords or account numbers by looking over someone'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 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 administrators would have to restart it or make repairs. Other times, when these intruders were again denied access once their activities were discovered, they would react with purposefully destructive actions. When the number of these destructive computer intrusions became 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 “computer criminal,” the media began using the term “hacker” to describe individuals who break into computers for fun, revenge, or profit. Since calling someone 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 “criminal 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 governments. They want to be able to take advantage of the Internet for electronic commerce, advertising, 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 maintaining control of personal information that varies from credit card numbers to social security numbers and home addresses.
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 interests would be to have independent computer security professionals attempt to break into their computer systems. This scheme is similar to having independent auditors come into an organization to verify its bookkeeping records. In the case of computer security, these “tiger teams” or “ethical hackers” 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 report 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 operating systems for “potential use as a two-level (secret/top secret) system.” Their evaluation found that while Multics was “significantly better than other conventional systems,” it also had “ … vulnerabilities in hardware security, software security, and procedural 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 access that an intruder could potentially achieve. They performed tests that were simple information-gathering exercises, as well as other tests that were outright attacks upon the system that might damage its integrity. Clearly, their audience wanted to know both results. There are several other now unclassified reports that describe ethical hacking activities within the U.S. military.
With the growth of computer networking, and of the Internet in particular, computer and network vulnerability studies began to appear outside of the military establishment. Most notable of these was the work by Farmer and Venema, which was originally posted to Usenet in December of 1993. They discussed publicly, perhaps for the first time, this idea of using the techniques of the hacker to assess the security of a system. With the goal of raising the overall 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, packaged them in a single, easy-to-use application, and gave it away to anyone who chose to download it. Their program, called Security Analysis Tool for Auditing 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 capabilities were misunderstood. The tool was not an automated hacker program that would bore into systems and steal their secrets. Rather, the tool performed an audit that both identified the vulnerabilities of a system and provided advice on how to eliminate them. Just as banks have regular audits of their accounts and procedures, computer systems also need regular checking. The SATAN tool provided that auditing capability, but it went one step further: it also advised the user on how to correct the problems 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?
Successful ethical hackers possess a variety of skills. First and foremost, they must be completely trustworthy. While testing the security of a client's systems, the ethical hacker may discover information about the client that should remain secret. In many cases, this information, if publicized, could lead to real intruders breaking into the systems, 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 hackers themselves: limited-access labs with physical security protection and full ceiling-to-floor walls, multiple 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 programming and computer networking skills and have been in the computer and networking business for several years. They are also adept at installing and maintaining systems that use the more popular operating systems (e.g., UNIX or Windows NT ) used on target systems. These base skills are augmented with detailed knowledge of the hardware and software provided by the more popular computer and networking 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 management skills are necessary for the actual vulnerability testing, but are equally important when preparing 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 movies, 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 evaluation may require several days of tedious work that is difficult to automate. Some portions of the evaluations 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 opponent is vital to your success. In the computer security realm, the ethical hacker's task is the harder one. With traditional crime anyone can become a shoplifter, graffiti artist, or a mugger. Their potential 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. Ethical hackers have to know the techniques of the criminal hackers, how their activities might be detected, and how to stop them.
Given these qualifications, how does one go about finding such individuals? The best ethical hacker candidates will have successfully published research papers or released popular open-source security software. 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 liberal arts, who took it personally when someone disrupted 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 eliminated 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 parents of the students really feel comfortable with such a choice? This decision was further justified when the service was initially offered: the customers themselves asked that such a restriction be observed. Since IBM's ethical hacking group was formed, there have been numerous ex-hackers who have become security consultants and spokespersons for the news media. 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:
- What can an intruder see on the target systems?
- What can an intruder do with that information?
- Does anyone at the target notice the intruder's attempts or successes?
While the first and second of these are clearly important, the third is even more important: If the owners 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 answers to questions similar to those posed by Garfinkel and Spafford:
1. What are you trying to protect?
2. What are you trying to protect against?
- How much time, effort, and money are you willing to expend to obtain adequate protection?
A surprising number of clients have difficulty precisely answering the first question: a medical center might say “our patient information,” an engineering firm might answer “our new product designs,” and a Web retailer might answer “our customer database.”
All of these answers fall short, since they only describe 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 affect the organization or its clients. These assets should also include secondary information sources, such as employee names and addresses , computer and network information (which could provide assistance to an intruder), and other organizations with which this organization collaborates (which provide alternate paths into the target 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 unavailable. The world became quite familiar with denial-of-service attacks in February of 2000 when attacks 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 organization's computer. The level of damage to an organization's good image resulting from a successful criminal hack can range from merely embarrassing to a serious threat to revenue. As an example of a hack affecting an organization's image, on January 17, 2000, a U.S. Library of Congress Web site was attacked.