McAfee struggles to explain Windows XP anti-virus blunder

After distributing a buggy antivirus update that apparently disabled hundreds of thousands of computers on yesterday, McAfee is still at a loss to explain exactly what happened.

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After distributing a buggy antivirus update that apparently disabled hundreds of thousands of computers on yesterday, McAfee is still at a loss to explain exactly what happened.

McAfee says that just a small fraction of its corporate customers -- less than 0.5 percent -- were affected by the glitch, which caused some Windows XP Service Pack 3 systems to crash and reboot repeatedly. McAfee blamed a bad virus definition update shipped out Wednesday morning, Pacific time, which ended up quarantining a critical Windows process called svchost.exe.

By the end of the day, the antivirus vendor still couldn't say exactly what caused the problem. "We're investigating how it was possible some customers were impacted and some not," said Joris Evers, a McAfee spokesman, speaking via instant message. One common factor amongst the victims of the glitch, however, is that they'd enabled a feature called "Scan Processes on Enable" in McAfee VirusScan software.

Added in version 8.7 of the product, this feature lets McAfee's malware scanner check processes in the computer's memory when it starts up. According to Evers, it is currently not enabled by default. However, some versions of VirusScan did ship with it enabled. McAfee's instructions for repairing affected computers can be found here.

A large number of users reported major problems after installing McAfee's bad update Wednesday.

Systems at Intel were knocked offline before the bad update could be stopped, according to Intel spokesman Chuck Mulloy. He couldn't say how many PCs were affected, but said that the problem was "significant."

"There were quite a few clients, laptops and PCs [affected]," he said. "We were able to get it stopped fairly early on, but clearly not soon enough."

The problem took out PCs at about 40 percent of the customers of UK-based IT outsourcing company Centrality, according to Managing Director Mike Davis. "It's absolutely massive in terms of what we're seeing here," he said.

The problem started late in the afternoon, Davis said. "We started getting calls about 4 p.m. U.K. time on our help desk from customers that were having their XP-based machines just reboot seemingly randomly," he said. After realising that it was happening to several different customers simultaneously, Centrality quickly figured out that the problem had to do with McAfee's update, and started shutting down McAfee ePolicy Orchestrator management servers to keep the problem from spreading. By then, however, several thousand computers had disappeared from the networks it manages.

Because the update knocked PCs offline that meant that there was no easy way to fix the broken computers over the network, so harried system administrators had to either walk users through the repair process or fix the infected machines themselves, one by one.

For many the problem was strangely similar to a widespread virus outbreak.

It's not unheard of for antivirus vendors to mistakenly flag legitimate software with their updates. Criminals have become so good at switching up their code that companies like McAfee are now churning out millions of signatures in a cat-and-mouse game to identify malware that is in circulation. That leads to errors.

Still, that McAfee allowed a major Windows component to be misidentified demonstrates "a complete failure in their quality control process," said Amrit Williams, CTO with systems management vendor BigFix. "You're not talking about some obscure file from a random third party; you're talking about a critical Windows file," he said. "The fact that it wasn't found is extremely troubling."

Late Wednesday, McAfee's executive vice president of support, Barry McPherson, posted a short note saying that he had "talked to literally hundreds of my colleagues around the world and emailed thousands to try and find the best way to correct these issues."

He didn't apologise to customers but added, "Let me say this has not been my favorite day. Not for me, or for McAfee. Not by a long shot."

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