Some Mac owners have been skeptical of the claims that Flashback has infected hundreds of thousands of machines, and have accused antivirus vendors like Dr. Web and Kaspersky -- the two Russian companies that have calculated the extent of the malware infection -- of hyping the threat to sell software.

One Sophos executive addressed those critics in a today.

"For those of you inclined to let rip in the comments that I'm only discussing Mac malware, and talking up the risks, because we happen to have a free product to 'sell' you, please consider an alternative explanation," argued Paul Ducklin, who heads Sophos Asia-Pacific technology team. "Perhaps the reason we have a free product to 'sell' is because we think there is a genuine risk?"

Flashback had that used Dr. Web's free checking tool, and the malware's makers currently control more than 650,000 systems.

Apple, which updated Java for Mac OS X on April 3 to quash the bug Flashback has been exploiting, promised yesterday to release a , probably within the next week.