Size: 289KB
BlastBack was designed to allow users to help out fellow users that are infected with the MSBlast (and variants) worm by sending them a message (via the Windows' Messenger service) telling them that they appear to be infected with MSBlast as their machine attempted to connect to port 135.
Size: 100KB
It is a free removal tool from Symanted to remove infections of all known variants of W32.Klez@mm, as well as all known variants of W32.Elkern.