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Article in Science

Posted by isilanes on November 15, 2006

I have just read a rather interesting article in Science about the economics of information security (R. Anderson and T. Moore, Science, 2006, 314, 610), and I would like to comment some quotes of it:

There has been a vigorous debate between software vendors and security researchers over whether actively seeking and disclosing vulnerabilities is socially desirable. Rescorla has argued that for software with many latent vulnerabilities (e.g. Windows), removing one bug makes little difference to the likelihood of an attacker finding another one later[1].

Quite interesting! First, even a paper on Science not only regards Windows as a piece of software with a virtually endless reservoir of internal errors, but it even uses it as a paradigmatic example of such a case. Second, it deems such software as not worth patching, and bugs not worth being disclosed (security through obscurity), because they are so many.

[…] [Rescorla] argued against disclosure and frequent patching unless the same vulnerabilities are likely to be rediscovered later. Ozment found that for FreeBSD[2] […] vulnerabilities are indeed likely to be rediscovered[3]. Ozment and Schecher also found that the rate at which unique vulnerabilities were disclosed for the core and unchanged FreeBSD operating system has decreased over a 6-year period[4]. These findings suggest that vulnerability disclosure can improve system security over the long term.

I have read [1] and [3] very briefly, and Ozment seems very critical of Rescorla’s results. However, the comparison between Windows and FreeBSD (I think they mean OpenBSD), which is FLOSS, is quite nice. Windows is so buggy that patching it is hopeless. FreeBSD has seen a decline in the number of disclosed bugs (remember that, being FLOSS, all the bugs found by developers, mantainers and users are disclosed), related to the fact that each bug fixed actually means a reduced probability of finding new bugs (because the total is not endless).

The bottom line is that, for a good piece of software (one that is not so bug-ridden that crackers never “rediscover” an old bug, because there are sooo many new ones to discover), disclosing the bugs is better. It is so because it speeds the patching rate, which in turn reduces the amount of exploitable bugs, which in turn improves the security. The connection between patching bugs and reducing significantly the amount of exploitable bugs can be made when the amount of bugs is small enough that new crackers are likely to rediscover old bugs, and then it would have paid to patch those bugs. Notice also that this is an auto-catalytic (self-accelerated) process: the more bugs disclosed, and more bugs patched, the less bugs remain, so the more it pays to further disclose and patch the remaining bugs, because the less bugs, the relatively more it pays to patch.

Vulnerability disclosure also helps to give vendors an incentive to fix bugs in subsequent product releases[5]. Arora et al. have shown through quantitative analysis that public disclosure made vendors respond with fixes more quickly; the number of attacks increased, but the number of reported vulnerabilities declined over time[6]

Good point! Not only disclosing the bugs is good for the consumers because it directly increases its quality, but also because it helps enforce a better behavior of the vendors. This is a key idea in the article, which delves in the fact that security policies are best when the one enforcing them is the one suffering from their errors. However, nowadays there is little pressure on the vendors to produce more secure software, because the buyer has little knowledge to judge this aspect of the quality, and ends up favoring a product for its looks or the alleged features, regardless of stability or security. Disclosing the bugs helps the buyer to assess the security of a program, thus making a better-balanced choice when buying. This, in return, leads to a more secure software in general, because vendors will have a big incentive to make their products more secure (which they don’t really have now).

[1] E. Rescorla, paper presented in the Third Workshop on the Economics of Information Security, Minneapolis, 13 to 14 May 2004 (PDF)
[2] I suspect the authors are mistaking OpenBSD for FreeBSD
[3] A. Ozment, paper presented at the Fourth Workshop on the Economics of Information Security, Cambridge, MA, 2 to 3 June 2005 (PDF)
[4] A. Ozment, S.E. Schechter, paper presented at the 15th USENIX Security Symposium, Vancouver, 31 July to 4 August 2006 (HTML).
[5] A. Arora, R. Telang, H. Xu, paper presented at the Third Workshop on the Economics of Information Security, Minneapolis, 13 to 14 May 2004 (PDF)
[6] A. Arora, R. Krishnan, A. Nandkumar, R. Telang, Y. Yang, paper presented at the Third Workshop on the Economics of Information Security, Minneapolis, 13 to 14 May 2004 (PDF)

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