The Symantec link that Aussiebloke gave says:
The virus/worm W32.Magistr.24876@mm can arrive as an attachment named Sulfnbk.exe. The Sulfnbk.exe file used by Windows is located in the C:\Windows\Command folder. If the file is located in any other folder, or arrives as an attachment to a email message, then it is possible that the file is infected.
Just checked, and mine is in the right place.