Brother's computer got infected by this. MS Security Essentials was running and fully updated but did not stop it, in fact, it stopped SE. I ran the AVG bootable cd. It could not find or stop SecurityTool. I did some detective work to find and delete the files and the registry entries. I installed and ran Malwarebytes Anti-Malware. It seems to be gone. Brother says the only thing he was doing was playing Farmville. I read that Zynga's toolbar got hacked to display some Russian site, this might have also been slipped in.