It has been seven weeks since the "Mac Defender" malware first gained significant publicity, and we've seen Apple in response step up its anti-malware efforts with the release of a security update late last month that not only addressed the known Mac Defender variants at that time but also introduced daily checks for new malware definitions. The action significantly expanded the rudimentary anti-malware capabilities introduced with the launch of Mac OS X Snow Leopard.
The creators of the "Mac Defender" malware have not, however, given up in the face of Apple's increased defenses, moving within hours to release a new variant evading detection. Apple responded quickly, however, adding new definitions to detect the variant within a day.
That cat-and-mouse game has continued for the past three weeks, with Apple issuing new malware definitions on a nearly daily basis and the File Quarantine functionality defined by Apple's updated Xprotect.plist file now detecting 15 different variants of Mac Defender. While reports of users falling for the ruse and installing Mac Defender have declined in recent weeks as increasing numbers of users have installed the security update and had their anti-malware definitions updated, some users are still reporting difficulties stemming from the software.
Consequently, it seems reasonable to conclude that Apple has significantly eaten into the profitability of the existing Mac Defender scam, but it is unclear whether the malware writers will simply continue to slightly tweak the existing implementation and infect however many computers they can before Apple quickly updates the definitions or if they (and undoubtedly others) have broader plans in mind now that they have determined how Apple is addressing the threat.