From the SANS Internet Storm Center:

[snip] Starting around 11:30 UTC, we've received several reports on a new worm variant that makes use of MS05-039 to spread. If you're not patched yet, this is your last call. F-Secure named the critter "Zotob.A",http://www.f-secure.com/weblog/ We've also received a submission of a binary called "pnpsrv.exe", which is recognized by ClamAV as Trojan.Spybot-123. Another reader has contributed evidence that a successful exploit by Zotob.A (or variant) 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. [snip] http://isc.sans.org/diary.php?date=2005-08-14 - ferg -- "Fergie", a.k.a. Paul Ferguson Engineering Architecture for the Internet fergdawg@netzero.net or fergdawg@sbcglobal.net ferg's tech blog: http://fergdawg.blogspot.com/