The spike in downloads and sales didn't surprise Stephen Baker, an analyst with the NPD Group, which tracks retail software sales in the U.S.
Although NPD doesn't have sales data on Mac antivirus software during the last week -- it takes the company longer than that to acquire and compile the numbers -- Baker said there's a strong link between security threats and sales.
"Historically, we have always seen a jump in security sales that correlate to highly publicized security issues," said Baker in an email reply to questions. "[But] the spike seems to be declining over the years as more consumers use and recognize the importance of security software."
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 blog post 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 infected nearly 2% of the Macs that used Dr. Web's free checking tool, and the malware's makers currently control more than 650,000 systems.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed. His email address is email@example.com.