A recent security update from antivirus company McAfee has resulted in an estimated "hundreds of thousands" of crashed Windows XP computers. The issue appears to be widespread, causing PCs to crash, freeze, or be stuck in and endless reboot loop, thereby rendering the PCs completely unusable.

The impact of the malicious update thus far has been staggering. According to the University of Michigan's medical school, almost 1/4 of its PCs (8,000 of 25,000) crashed after the update was applied. The Lexington, Kentucky police force reported shortly afterwards that it had been forced to hand write reports because of the issue.

Although McAfee suggests that "less than 0.5 percent of customers affected by [the buggy 5958 DAT update]," there are already thousands of posts online complaining of the issue, with just as many IT departments scrambling for a fix. (Source: computerworlduk.com)

XP SP3 Machines Affected by McAfee Update

The update crash targeted XP machines running Microsoft's Service Pack 3 (SP3).

McAfee's update is falsely identifying legitimate processes (such as SVHOST.EXE) as the actions of a virus, terminating them, which causes the entire operating system to crash. (Source: pcmag.com)

McAfee Works Towards 5958 Fix

McAfee has confirmed the problem and has replaced the problematic update code with a new version.

"McAfee is aware that a number of customers have incurred a false-positive error due to incorrect malware alerts on Wednesday, April 21," the company said in a statement. "The problem occurs with the 5958 virus definition file (DAT)." (Source: cnet.com)

Thus far, the update is not causing problems for systems running Microsoft's other, newer operating systems, Windows Vista or Windows 7.

If you've downloaded the problem update and are looking for a fix, McAfee has posted a fix, though it is technical. It recommends manually downloading and installing a new "EXTRA.DAT" file that restores files improperly quarantined by the antivirus software.

It's not the easiest solution to follow, and as such McAfee promises it is working on something better for a broader range of users.