The following free Microsoft software detects and removes this threat:
Run the Microsoft Safety Scanner
If you're having trouble cleaning Win32/Sirefef, the Microsoft Safety Scanner may help you remove it:
After you've used the Microsoft Safety Scanner, you should make sure your security software is up to date and run a full scan:
Even if we've already detected and removed this particular threat, running a full scan might find other malware that is hiding on your PC.
Note that as part of the cleaning, our software might change some Windows services back to their default settings. If you had previously changed these settings, you might need to change them again.
The services that are reset include:
BFE – Base Filtering Engine
Iphlsvc – IP helper Service
MSMpSvc – Microsoft Antimalware service – MSE/FEP/SCEP
Sharedaccess – Internet Connection Sharing
WinDefend – Microsoft Antimalware service
Wscsvc - Windows Security Center
You can also visit the Microsoft virus and malware community for more help.