http://www.computerworld.com/securitytopics/security/story/0,,102307,00.html Opinion by Jian Zhen JUNE 08, 2005 COMPUTERWORLD Security through obscurity is probably one of the oldest tricks in the security book. The basic premise stems from the fact that people are trying to ensure security by hiding certain facts of their software or architecture design from regular users. This is equivalent to someone hiding a house key under a pot of plants in front of his house. However, Auguste Kerckhoffs, a 19th century Flemish cryptographer, said it should be assumed that attackers know the design of the entire security system, except for the keys. This concept, known as Kerckhoffs' law, basically rejected the notion of security through obscurity (your key hidden under your potted plant) and suggested that a system should be secure even if everything's public knowledge, except the key. Most administrators and developers these days are somewhat familiar with the various security concepts such as virus, worm, buffer or heap overflow, cross-site scripting and SQL injection. Since these concepts are fresh in their minds, they try to take explicit precaution to avoid these traps. However, they continue to develop software and products that rely on hiding certain trivial information, such as URL, username or other session information, and hope that users won't find them. They also try to hide this information in obvious places, such as hidden fields of a Web page or a different directory on a Web server. A case in point: Last March, Harvard Business School, along with a few other top business schools, suffered a huge embarrassment because its admission portal had a "break-in," as university officials called it (see story) [1]. ApplyYourself.com, a company that handles applications for Harvard and other elite institutions, had a Web portal where applicants could check on the status of their applications. Generally, Harvard's decisions go out on March 30. However, one applicant had figured out a way to obtain the status before that date. This applicant then posted it on a Web site for others to try. In the end, a total of 119 applicants tried this method. After finding out, Harvard decided to reject these 119 applicants regardless of their admission status (see story) [2]. Stanford University had made similar decisions recently, rejecting 41 applicants who tried this method. Lessons learned We are not here to argue whether Harvard and Stanford made the right decision or whether the action taken by the 119 applicants was ethical. However, there are some lessons to be learned here. First of all, ApplyYourself.com's method of hiding the admission status from the applicants was a great example of security through obscurity. In order to obtain the status early, the users took information that was readily available to them, modified the URL in their browsers and got access to their own admission status. There are at least two major mistakes here. First, ApplyYourself.com hid an ID field that users were not supposed to see in the Web page source. This ID was then used to construct the URL that would give the user the admission status. Second, ApplyYourself.com assumed that users would not have knowledge of the URL that would provide the status. However, anyone who applied to these schools through ApplyYourself.com would have seen the URL, and would have known what the URL looked like, as well as the parameters required to construct the URL. Given that this URL was provided to previous applicants, current applicants could easily obtain it by simply asking. These two grave mistakes left ApplyYourself.com scrambling to patch the security holes. Another good example of security through obscurity was demonstrated when hackers compromised Cisco Systems Inc.'s corporate network and stole more than 800MB of source code (see story)[3]. This incident caused quite a stir in the IT community, since Cisco's routers are responsible for managing a majority of the Internet traffic. Any security issues in the source code could become public. The publication of these security vulnerabilities -- still a possibility -- has the definite potential of causing major havoc on the Internet, possibly bringing it down on its knees. Microsoft Corp. has also experienced similar embarrassing incidents. In February 2004, portions of the source code for the Microsoft Windows NT and Windows 2000 operating systems were leaked (see story)[4]. The leaked source code could potentially allow hackers to identify security vulnerabilities in the Windows operating systems. Given the popularity of Windows in both consumer and corporate environments, this leak could be devastating to the whole Internet community. All these examples demonstratem the danger of the security-through-obscurity premise. There are many articles, books and seminars on this topic. Companies and software developers need to start with Kerckhoffs' law, assume that the algorithm and design of the software are known, and design security into the products and software in the beginning instead of retrofitting or patching security holes later. [1] http://www.computerworld.com/securitytopics/security/story/0,10801,100206,00.html [2] http://www.computerworld.com/databasetopics/data/story/0,10801,100261,00.html [3] http://www.computerworld.com/securitytopics/security/story/0,10801,93215,00.html [4] http://www.computerworld.com/softwaretopics/os/story/0,10801,90200,00.html _________________________________________ Attend the Black Hat Briefings and Training, Las Vegas July 23-28 - 2,000+ international security experts, 10 tracks, no vendor pitches. www.blackhat.com
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