The researcher said that out of 236,000 known pieces of malicious software, only seven affect Mac OS X. "With an estimated OS X market share of about five per cent on desktop systems we would expect to see more malware for OS X," said van Oers.

"Malware writers tend to write for systems that are the mostly widely used," he writes. "With Microsoft Windows being dominant in the desktop market it is clear why the most malware is written for it. Also, prior to Vista, the various Windows versions were pretty much wide open, full access, making it relatively easy for malware to abuse."