updated 12:10 pm EDT, Mon May 2, 2011
Attack dependent on user gullibility
Mitigating the seriousness of the threat is that the malware requires people to accept installation and provide an administrator password. It is also possible to disable automatic launch of downloaded files, assuming the option has been turned on in a browser in the first place. Apple support forum posters observe that it's possible to scrub the malware by killing processes in Activity Monitor and then dragging MACDefender from the Applications folder to the Trash.
The software coincidentally shares a name with a small company responsible for two apps, GCStatistic and DTmatrix. The outfit denies any association with the malware. "I would never release an application named like this," MacDefender's operator says.