WINDOWS: Security Update for Microsoft Windows (MS04-012 | KB828741)
While not as bad as the last one, this update patches 4 vulnerabilities in Windows. Specifically, these deal with the systems that let programs run and talk to each other across several other computers. It was a vulnerability in thses systems that allowed MSBlaster to wreak havok, so make sure you install this patch immediately. Windows XP Service Pack 2 RC1 is not affected.
Patches: Windows Server 2003 (64-Bit) | Windows Server 2003 | Windows XP (RTM & SP1) | Windows 2000 SP2, SP3, & SP4 |