Fake Antivirus is on the rise. This threat tricks
users into believing your computer is infected and alerts you to to install a
cleaner or scanner. The threat appears as a legitimate looking windows
alert and is effective by creating a sense of sudden decision making on what
to do...
Be aware no antivirus software can protect from this threat since new
variants are seen every day. Symantec has a great educational page on
this threat
seen here.