As users become smarter in distinguishing the name of fake and real antivirus programs, rogueware authors have now resorted to a bolder move — stealing the identity of a legit program and using it on their fake products. A rogue was recently discovered to be using AVG's logo and reputable name, hoping to mislead and trick people into purchasing the fake AV.
It implemented the typical method used by other rogues, i.e., pretending to scan the system and then claiming to have detected multiple malicious files. Since the free version is limited in capability, users have to upgrade to the full (fake) version to remove these files.
Aside from AVG's logo, the rogue's interface bears no resemblance to that of the legit AVG Anti-Virus Free Edition 2011.
However, users who aren't familiar with the product might not notice this difference and think that they are getting the real thing.
One bit of advice — watch out for the source. Most antivirus companies provide free/trial versions of their products directly on their websites. So, skip the untrustworthy channel and get it directly from the AV vendors.