Microsoft yesterday again put the scare into Windows XP users, telling them that after April 8, 2014, the chance that malware will infect their PCs could jump by two-thirds.

The claim, made by Tim Rains, director of Microsoft's Trustworthy Computing group, came on the heels of the release of the company's twice-annual Security Intelligence Report.

Following up on comments he made in August, Rains again warned Windows XP stragglers to expect an increase in attacks when the aged operating system exits support in five months.

"After end of support, attackers will have an advantage over defenders who continue to run Windows XP," Rains asserted in a Tuesday post to a company blog. "After April next year, when we release monthly security updates for supported versions of Windows, attackers will try and reverse engineer them to identify any vulnerabilities that also exist in Windows XP. If they succeed, attackers will have the capability to develop exploit code to take advantage of them."

Rains then went a step further, and cited statistics from Microsoft's own telemetry-gathering efforts to give customers an idea of the increased threat after support ends.

"We have already had a glimpse into what happens when a Windows XP-based platform goes out of support," Rains added. "In the two years after Windows XP Service Pack 2 went out of support, its malware infection rate was 66% higher than Windows XP Service Pack 3 -- the last supported version of Windows XP."

Support for Windows XP Service Pack 2 (SP2) ended in July 2010, a little over two years after the release of XP SP3.