Microsoft confirmed on Friday that it will continue to offer its malware scrubbing program to Windows XP users for more than a year after it stops patching the operating system.

"Microsoft's Malicious Software Removal Tool is aligned with the company's anti-malware engines and signatures, and as such the removal tool will continue to be provided for Windows XP through July 14, 2015," a company spokesperson wrote in an email reply to questions.

The Malicious Software Removal Tool (MSRT) is updated monthly as Microsoft targets specific major malware families it believes are the biggest threats at the time. It's distributed through Microsoft's Windows Update service and the business-grade Windows Server Update Service (WSUS) on "Patch Tuesday," the date each month when the company ships security patches and other fixes to customers. The MSRT automatically installs and then runs in a seek-and-destroy mission.

Users can also manually download the MSRT from Microsoft's website.

MSRT is not an antivirus program, but rather a cleanup utility designed to eradicate malware that has already wormed onto a Windows PC. The tool was first released in 2005.

The extension of MSRT's availability for Windows XP was part of Microsoft's decision last Wednesday to offer new anti-malware signatures to XP customers who run the company's free Security Essentials antivirus (AV) software.

Originally, Microsoft had said it would stop shipping Security Essentials' signature updates to XP PCs after April 8. But in a tacit nod to XP's widespread use, Microsoft postponed the cut-off until July 14, 2015.

Microsoft will ship its final public security patches for Windows XP in less than three months, ending nearly 13 years of support for the ultra-successful OS.

Microsoft did not reply Saturday to follow-up questions asking what channels it will use to distribute the malware eraser between April 8, 2014, and July 14, 2015.

If Microsoft continued to deliver the MSRT via Windows Update, the tool would be a valuable weapon in containing infections on Windows XP PCs.

Say a new malware family popped up, or an older one began infecting large numbers of Windows PCs, including those still running XP. Microsoft would be able to revise MSRT so it targets the new or suddenly aggressive malware for detection and deletion, and automatically put it on XP systems. Not only would that keep the remaining XP owners safer, but it would also reduce the number of compromised computers that could in turn be used by hackers to infect machines running the still-supported Vista, Windows 7 and Windows 8 operating systems.

The impact of the MSRT extension would be more muted if Microsoft required users to download the tool themselves. Even so, MSRT is a very popular download -- currently No. 2 on the company's Download Center -- indicating that large numbers of customers seek it out.

Although Microsoft has been urging customers to drop XP before the April 8 deadline for a new OS or PC, millions of machines worldwide will continue to run the aged OS for months and maybe even years to come.

According to metrics company Net Applications, Windows XP's user share -- the percentage of all personal computer owners who went online with that OS -- stood at 29% at the end of December 2013. Computerworld has forecast that at least 25% of all personal computers will be running the operating system at the end of April, and about 20% at the end of this year.

Those numbers were at the root of Microsoft's recent moves to help out XP users: While the company has remained adamant that bug patches will be discontinued after April 8, some cracks in its "Death to XP" policy have appeared, including the continued availability of Security Essentials' signatures and the lifespan extension for the MSRT.

The explanation: Microsoft has decided it best for all concerned -- including itself and its reputation -- that it throw some security bones, if only small ones, to those who can't or won't upgrade from XP.

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 gkeizer@computerworld.com.

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