This must be a Windows problem. I could find nothing that says it is happening on a Mac unless maybe somebody is running Windows on a Mac and not Mac OS. So 22 messages into the thread I guess it is time for someone to chime in, "Get a Mac!"
This is a Trojan that 'calls home'. It gives the hacker remote & complete
control of your system and/runs other malware that hooks your system to their server; deletes certain require Windows & networking files to prevent most users from doing his own repair; sets a MBR that on reboot will re-connect to their server & redo any changes you have attempted; set a blank blue screen (usually it just looks like the Blue Screen of Death) with the 'extortion' message for money; ... believe me ... the A-hole has already downloaded all of your personal data to find credit card & banking info later at this point.
The same can be done to Macs, just their are not enough Mac systems for most hackers to want to learn.So this is not just a Windows problem.
It was suggested above to keep a separate Linux system to just trash when getting the virus, the same can be done with Windows. ... Keep your file backed up to another system at home. Then you can just reload windows if need be without having to call a 'Comp Guru'.
OR, ... for laptops, have a spare 'cloned' HD with your files ready to go. Just swap the Drives; wipe the bad one and clone to the good drive.
A 'boot' USB drive with Windows is also good to have. This will restart a sytem and repair a MBR.