FakeAVers are playing on the media hype and the sometimes exagarated infection reports to peddle their wares. Once visited or downloaded, the FakeAV window appears, be it flash, javascript or an actual executable, and warns you of the impending doom if you do not make the small investment of $29.95 to rid your apparently infected computer of the nasty malware the media has been talking about. After all, they are just following good security practice! And lets face it, for that warm fuzzy feeling of knowing youre once again safe and protected in this world of Trojans, worms, viruses and malware.”]
Source: https://nakedsecurity.sophos.com/2009/01/29/fakeav-exploits-greymatter-vulnerability/