Sophos, which sells security software only to enterprises and organizations, also offers a free Mac product to consumers: .

Several other companies that sell Mac security software, including Symantec and F-Secure, did not reply to questions about their recent sales trends.

But statistics from Apple's Mac App Store, the online market that launched in January 2011, hint at a strong increase in Mac antivirus interest.

BitDefender Virus Scanner, a free app in the Mac App Store, is currently No. 16 on the , down one spot from an earlier high of No. 15, according to AppShopper.com. BitDefender's app has been on that list for just 16 days.

Clam AV, another free antivirus program for the Mac, is at No. 14 today, down four spots from its highest point on the same list but up from No. 97 on April 2, two days before news of the Flashback infection began in earnest.