I did a little researching. Port 137 is used for Windows File and Printer sharing, but is also exploited by some worms/trojans/backdoors. These are just a few:

  • W32.HLLW.Moega
  • W32.Crowt.A@mm (01.23.2005) - mass mailing worm, opens a backdoor, logs keystrokes. Uses ports 80 and 137.

W32.Reidana.A (03.27.2005) - worm that spreads using the MS DCOM RPC vulnerability (MS Security Bulletin [MS03-026]) on port 139. The worm attempts to download and execute a remote file via FTP. Opens TCP port 4444.

Just a little food for thought.