Zotob.A is a worm targeting Windows 2000–based systems which takes advantage of a security issue that was addressed by Microsoft Security Bulletin MS05-039. This worm installs malicious software, and then looks for other computers to infect.
Important If you have installed the update released with Security Bulletin MS05-039, you are already protected from Zotob.A. If you are using any supported version of Windows other than Windows 2000, you are not at risk from Zotob.A ...
Leggi:
http://www.microsoft.com/security/incident/zotob.mspx