Believe it or not, some types of malware actually masquerade as anti-malware tools, confusing even seasoned computer users. It's the ultimate bad joke when it comes to viruses.
These programs, called "rogue scanners" or sometimes "scareware" look incredibly realistic, displaying well designed virus warnings, realistic scanning activity, and often instructions to purchase the "full version" of the program to remove the list of found viruses which, of course, aren't really there because the warning itself is the virus.
Confused? That's the point.
Mary Landesman, About.com Guide to Antivirus Software, has an excellent writeup about these dangerous but incredibly clever forms of malware:
informative stuff, thanks