Data released today by Microsoft showed that Windows 7's malware infection rate climbed by more than 30% during the second half of 2010, even as the infection rate of the 10-year-old Windows XP fell by more than 20%.

"Infection rates have jumped [for Windows 7]," admitted Jeff Williams, the principal group program manager with the Microsoft Malware Protection Center (MMPC). "We attribute that to the increased presence of malicious software attacks out there."

For the second half of 2010, 32-bit Windows 7 machines were infected at an average rate of over 4 PCs per 1,000, a 33% increase over the approximately 3-per-1,000 infection rate during the first half of the year.

PCs running the 64-bit version of Windows 7 fared slightly better, with an infection rate of 2.5 per 1,000 during all of 2010.

The infection rates were tabulated from scans conducted by the Malicious Software Removal Tool (MSRT), a free utility updated monthly and pushed to Windows users via Microsoft's update services. MSFT detects and deletes selected malware, including fake antivirus programs, worms, viruses and bot Trojans.

Full story: Computerworld