Chasing A Moving Target

Coping with a Microsoft "Black Tuesday" is bad enough when there's 28 vulnerabilities being patched, but add to it a zero day vulnerability in Internet Explorer 7 (IE) that's being exploited in the wild and it could turn into a pretty bad week. Since none of the patches released by Microsoft during their normal December patch cycle address the exploited vulnerability, enterprises are left with almost no mitigation options to protect their users until Microsoft does release a patch...possibly a month from now.

The current predicament leaves us wondering two things; will Microsoft release another out-of-cycle like they did with MS08-067 that was also being exploited in the wild, and how do we prevent our users from being exploited? I'm a little unsure about the first question considering the ramifications of having a currently exploited unpatched vulnerability floating out there. I'm sure MS will receive considerable heat since there are so many organizations where IE is the only browser option because of a variety of reasons, many of which stem from enterprise web applications not being cross-platform.The second question is what's probably harder to answer than how Microsoft will respond. Dealing with a zero day exploit like this one is a moving target because it exploits a web browser that is installed on every fully updated and patched installation of Windows XP. The exploit could be placed anywhere. An exploited web site like what is being done now in several Chinese domains. HTML e-mail. HTML help pages. Heck, I guess if someone got creative they could even be include in a USB autorun.inf attack like those that have been popular lately (see here and here).

Antivirus (AV) and IDS vendors are going to be scrambling to find a way to accurately detect this attack but it's difficult since it can be delivered via Javascript and the typical signature-type detection is near impossible since the Javascript can be easily obfuscated to evade signatures. There have already been two rules released for Snort through the Emerging Threats project but they're easily evaded like AV sigs.

At this point, the best advice I've seen is enable DEP (Data Execution Prevention) on IE7 and block the known hosts serving up the attacks as identified in HD Moore's excellent analysis on the BreakingPoint Labs blog. If you get those things in place and keep an eye on sources like the SANS Internet Storm Center and your security vendors (both their update web page and blog if they have one), then hopefully you'll make it out on the other side without incident. Good luck.

John H. Sawyer is a Senior Security Engineer on the IT Security Team at the University of Florida. The views and opinions expressed in this blog are his own and do not represent the views and opinions of the UF IT Security Team or the University of Florida. When John's not fighting flaming, malware-infested machines or performing autopsies on blitzed boxes, he can usually be found hanging with his family, bouncing a baby on one knee and balancing a laptop on the other. Special to Dark Reading.