It comes from a rogue software group called FakeRean, and according to McAfee it poses as an antivirus, claiming it scanned your computer and you better hurry and buy this protection or your computer is going to break and the world is going to end. In reality, it took control of your GUI to extort money out of you using these scare tactics.
The renegade software is popping up on different version of Windows, morphing into whatever iteration of the operating system you're running on. Below is what you should be on the lookout for.
On Windows 7:
On Vista:
On XP:
Be wary of any software that urges you to buy antivirus protection—it very well may be an impostor. [McAfee via TheNextWeb]
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