The aftermath of the discovery followed a familiar pattern. Microsoft issued a patch on Jan. 5, 2006, in record time. But for a long while, unpatched computers running vulnerable versions of gdi32.dll roamed the Internet, slurping up mountains of malware.

The bug had far-reaching effects, enabling malicious code to be foisted on unsuspecting users and executed in a variety of ways: previewing an e-mail containing the malicious WMF file in Outlook; viewing an image preview in Explorer; viewing a malicious WMF in certain third-party graphics programs; indexing a hard disk that contained a malicious file; following a URL link in an e-mail, IM, or on another Web page to a site where the malicious file was embedded in the Web page.

Upshot: We learned that nothing is sacred, that any file format could be considered hostile. And we also got a cool new name for an exploit method: drive-by downloads.

MDAC: The component that keeps on giving (headaches)
Bug identifier: CVE-2006-0003, MS06-014
Description: Vulnerability in MDAC (Microsoft Data Access Components) could allow code execution
Alias: MDAC RDS.Dataspace ActiveX bug
Date published: April 11, 2006

Way back in 1998, Microsoft issued a security bulletin about a component of IIS that ran under Windows NT Server called Microsoft Data Access Components. In the bulletin, MS98-004, Microsoft warned that a part of MDAC called the RDS (Remote Data Service) had a vulnerability that allowed unauthorized people to browse databases.

Flash-forward eight years to the spring of 2006. Microsoft released a security bulletin about a component of MDAC called RDS, which has a vulnerability that permits malicious Web servers to perform drive-by downloads against the unpatched PCs of unsuspecting victims. Eerily familar.

In the later case, it was an ActiveX control that allowed users to connect to RDS through IE and wreak havoc. The ActiveX control doesn't behave as intended, and can be loaded and exploited if you visit the wrong Web site.

Of course, by 2006, MDAC isn't just loaded on servers; you may have it on your PC. Moreover, the bad guys have changed tactics. No longer content to wait patiently for you to happen upon their malicious Web site, they spam you with links, buy ads based on Google searches, and load their pages with SEO (search engine optimization)-rich keywords. The result, however, is the same: Visit and be exploited.

In fact, the bad guys are now using off-the-shelf exploit software to put malware onto your machine. A tool called MPack that's loaded on malicious Web sites can check to see what browser version you're using and what patches you have installed. Based on this analysis, it delivers the exploits that will do the most damage. More galling is that they don't even bother to hide what they're doing, naming the Web page that performs the exploit "mdac4.php."