Improvements in Office Security

We now have a pretty neat internal web site where I can easily search for CVE entries and bulletin counts by product. It shows some interesting trends that I hope will continue to hold. First, let me preface this by saying that CVE entry count is a better (though not perfect) way to measure how secure something is than bulletin count. We might sometimes package fixes for several CVE entries into one bulletin, and an older product might be vulnerable to all of them, but a newer product might only be vulnerable to around half.

We did a lot of work to make Office 2003 more secure in service pack 3 – one question I've had is just how much that's paid off? It has been about a year, and if I search from 9/18/2007 to 11/17/2008 (today), I get the following:


CVE count

Office 2000 SP3


Office XP SP3


Office 2003 SP2


Office 2003 SP3


Office 2007 Gold


Office 2007 SP1


The trending here is pretty clear – while we did a lot of good work to try and make Office 2003 more secure than previous versions, against the attacks we're seeing in 2007, it wasn't any better than Office XP. Now if you factor in huge amounts of work (no magic, no silver bullet, just lots and lots of work) that we did fixing fuzz bugs in Office 2007 and Office 2003 SP3, it looks like we've cut the incoming vulnerability rate by approximately half. If we look at it app-by-app, I think PowerPoint is a clear winner – they've had 5 CVE entries for older versions and only 1 for PowerPoint 2007 since 1/1/2007! Word has also done very well, dropping from 11 and 12 CVE entries in prior versions to only 2 for Word 2007 over the same period.

We're continuing to do that level of work on anything that still has a service pack left – next SP will be SP2 for Office 2007. It will be interesting to see how much additional gain that gives us. I'd like to see us do even better over time – while we've clearly made some significant gains, we still have more work remaining. We are currently doing about as many fuzzing iterations per weekend as we're required to do to meet SDL requirements for the entire product cycle (to be fair, the requirement is for clean runs, and we're not there yet, and when we do get there, we use a different fuzzer). We've done twice as many fuzz iterations against Office 2007 SP2 as we did against Office 2007 during the entire product cycle, and 4x more against Office 14 than against Office 2007.

If there's anyone out there still on Office 2003 SP2, I hope I've given you some convincing data that shows an upgrade to SP3 or better yet Office 2007 is going to pay off in much better security.