MS05-039 plug-and-play worm spotted in the wild

Yesterday I reported about a critical vulnerability in Windows which allows hackers to takeover your computer remotely and today SANS reports it has spotted the first worm on the Internet that takes advantage of this vulnerability.

Antivirus firm F-Secure cals the worm Zotob.A, while ClamAV refers to it as Trojan.Spybot-123. Windows 2000 users are advised to update as soon as possible. Windows XP SP2 and Windows 2003 users can't get hit by this worm as the worm does not use valid login.

The worm will download the main payload from the infecting machine. Once a machine is infected, it will become an ftp server itself. It will scan for open port 445/tcp. Once it finds a system with port 445 listening, it will try to use the PnP exploit to download and execute the main payload via ftp.

Important facts so far:
- Patch MS05-039 will protect you - Windows XP SP2 and Windows 2003 can not be exploited by this worm, as the worm does not use a valid logon.
- Blocking port 445 will protect you (but watch for internal infected systems)
- The FTP server does not run on port 21. It appears to pick a random high port.