Add, Group Policy Object Editor,
Add, Close, Ok.
Go to :-Local Computer Policy, User Configuration, Administrative Templates, System
Click on Systems
Double Click on "Don't Run Specified Windows Applications".
Select Enable and then click on Show, then Add
Add any applications you want to restrict. Blaster and Sobig.F are
Click OK and close out of the MMC.
These will help to stop the above two Trojan / worms.