"What is happening is that people are testing the waters," says Adam O'Donnell, chief architect of the cloud technology group at SourceFire and the author of the 2008 paper. "It just becomes economically viable to do it, so you start seeing these attacks becoming more common."

The 2008 paper used game theory to calculate when attackers would start seeing a payoff in focusing on the Mac OS X over Windows. It simplified the problem by assuming that . The assumptions helped reduce the problem down to two factors: the effectiveness of the defenses and the marketshare of the dominant platform.

With detection rates for antivirus in the 80 percent range, the Mac OS X becomes an attractive target around 16 percent marketshare. If PC defenses are better than 80 percent, then the Mac market share at which attackers become interested drops. For example, if antivirus programs detect attack 90 percent of the time, then attackers will focus on the Mac OS X at approximately 6 percent marketshare, says O'Donnell.

"It is much more of an argument that at the low rates of penetration of the Mac in the market is why there is no malware," he says. "You get a few points up, and like we are seeing now, you will start seeing malware."

Will the same model work to predict when significant malware will appear on smartphone handsets? Not necessarily. One of the assumptions is that the value of compromising a PC and Mac are identical. That assumption is less likely to hold up between a PC and a handset.