That sassy bug has a lot of spunk
Bug identifier: CVE-2003-0533, MS04-011
Description: Stack-based overflow in certain Active Directory service functions in LSASRV.DLL
Alias: The Sasser bug
Date published: April 13, 2004

In yet another example of ironic buffer-overflow goodness, this bug made the security subsystem of Windows the agent of evil itself. And, once again, malicious coders used Microsoft's own patch to figure out exactly where to target the OS.

As Windows XP's gatekeeper, LSASS (Local Security Authority Subsystem) manages the permissions of a PC's user accounts. So when eEye—the same company that discovered the Code Red bug—quietly disclosed the details of this flaw to Microsoft in October 2003, it touched off six months of furious coding in Redmond that culminated in a patch that fixed 13 other Windows 98, NT, 2000, XP, and Server 2003 flaws, as well as the LSASS bug.

And, within 18 days, the Sasser worm was cruising the Internet, hopping from one unpatched machine to another. The poorly coded worm wreaked havoc, shutting down networks around the world. Even though a fix was already available, many users—in particular, corporate IT managers—still had not applied MS04-011. By May 1, 2004, work on fixing the unintended damage caused by Sasser had become a round-the-clock operation, says then director of the Microsoft Security Response Center, Kevin Kean, with "a number of war rooms and rotating shifts" for MSRC staffers.

Upshot: What was that about patching as soon as the updates are available? Lessons that should have been learned three years earlier didn't really sink in until Sasser publicly pummeled patchless PCs to pulp.

WMF: Wherein malware is foisted
Bug identifier: CVE-2005-4560, MS06-001
Description: Vulnerability in graphics-rendering engine could allow remote code execution
Alias: Windows Metafile vulnerability, aka drive-by downloads
Date published: Jan. 5, 2006

Over the winter holidays in 2005, security researchers began discussing a newly discovered vulnerability in a Windows library used by the OS to display various kinds of graphics in apps and the OS itself.

The problem stemmed from a particular image file format, native to Windows since the days of Windows 3.0, called WMF (Windows Metafile). Used as the native format for storing graphics within Microsoft Office documents, support for WMF was by that point thoroughly embedded into Microsoft products.

WMF files contain function calls that a program sends to the GDI (Graphics Driver Interface). Someone discovered that WMF files can contain executable code as well. This would allow you to, say, create a WMF file that, merely by being viewing, invokes Internet Explorer to visit a particular URL, download a file, and execute that file. Special.