Hello lunfardo,
I would like to answer your issue and give you a clear understanding. Fake antivirus is methods were a programmer creates a well polished anti-virus program that is considered to be malware. So this makes the antivirus a hazard to your computers operating system and can greatly affect your system's performance by making the following affects:
Registry key deletion
System lock-up
Application access limitations
The common term for the fake anti-virus is "Scareware" and this terms comes from the affect which it gives when it pops up on your system to alert you of a virus, Trojan, spyware..Etc. Here is a link which will explain more in depth about the Fake antivirus:
http://www.sophos.com/en-us/security-news-trends/security-trends/fake-antivirus.aspx
(Note: The Url above has been provided for summary purposes only and the software link with the URL is not recommended for download as per this message post]
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