Intego, the makers of the VirusBarrier anti-virus software for the Mac, has issued a security warning that the supposed anti-virus software MacGuard is in reality itself malicious software:

• INTEGO SECURITY MEMO – October 17, 2008
• Macworld: Intego warns against MacGuard malware
• MacGuard knows malware because it is malware

Created by the same company that makes a Windows™ package called Winiguard:

which is both a scam that attempts to sell useless software and a dangerous rouge tool that “hijacks the user’s desktop and typically displays exaggerated or false claims of spyware found to frighten the user into paying for the program,”

Regarding MacGuard:

The software may be dangerous to Mac OS X, and there is a risk that the company “selling” this software may be scamming users and some sources suggest that they may be using the credit card numbers they harvest for nefarious purposes.