New Windows Worm on the Way?:
"The cycle began Tuesday when Microsoft Corp. released its monthly passel of patches, including one for a flaw in the Workstation service in Windows 2000 and XP. A successful exploitation would give the attacker complete control of the compromised PC, Microsoft said.."

Less than 24 hours after Microsoft issued the fix, two members of the BugTraq security mailing list posted exploit code for the vulnerability. The author of one of the exploits said the code had been tested only on a Windows 2000 machine with Service Pack 4 installed and the FAT32 file system running. The other exploit is designed for machines running Windows XP. However, experts said it would take little effort to adapt the code for other Windows machines.

And, more importantly, the Workstation vulnerability appears to be a prime candidate for a worm."

http://www.eweek.com/article2/0,4149,1382096,00.asp?kc=EWNWS111403DTX1K0000599