Ok from what I read it is a new Trojan (Some people just have too much time on their hands) discovered in mid December, which is why malwarebyes can't remove it because it does not know how
Sirefef, or ZeroAccess, is a Trojan that infects machines by exploiting a browser, through a third-party plugin, via an email attachment/link or it’s downloaded by other malicious software (malware). Once on the machine, it creates an environment where new threats can be installed without detection by most security software and then downloads these threats. Because it prevents antivirus software attempting to remove it, Sirefef is very difficult to remove, often requiring a complete system reinstall.
this may help
but if the system is compromised already i would reload from a clean backup but that's just my humble opinion because I have found many a time a lot of these 'removal tips or tools' are more trouble than they are worth...good luck