CVE Count and Statistics

Larry Seltzer had some interesting comments on my post about the rate of Office vulnerabilities at Vulnerabilities and Office Versions

There may be a little flaw in the analysis in that LeBlanc studied reports during the period from 9/18/2007 to 11/17/2008. By that time earlier Office versions had been around for a long time and many vulnerabilities had already been reported on them. But even so, it makes the numbers all the more impressive for the new versions; the older ones had already had the low-hanging fruit picked clean and yet they still had CVE numbers in excess of the new ones. It seems there is no low-hanging vulnerability fruit in new versions of Office.

Having had more grad school than I’d like to admit, I have a more than passing acquaintance with statistics. While there are certainly potential flaws in the numbers I posted, I don’t think this is one of them. I’ll argue that comparing vulnerability rates over the same time frame for two applications that are very similar, and which both have large market share, is better than comparisons of some number of days since release. If we have the same time frame, then the techniques used by the attackers are likely to be similar, and when we’re looking at multiple versions of the same thing, we can get a good estimate of how resistant one version is to attacks that another version is susceptible to.

What will be a problem in my analysis is how small the overall sample size is, and the fact that updates tend to ship at most 3-4 times per year for most of these apps. For example, this month’s set of bulletins are going to skew the results considerably, but the overall trend of substantial improvement will still show up. Once I get updated numbers, I’ll work them up and post them here.

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