This one caught me, managed to get rid of it using the latest update of VirusScan but it caused me a bit of hassle first! It's made the BBC news website as well.
A friend of mine without protection has it but cant delete the msblast.exe file in the system32 directory, anyone know how to get rid of it? He say's its not 'Read only' but won't delete?
If you haven't already I suggest everyone downloads the MS patch given in HugMonster's Post