McAfee Antivirus Update Wreaks Havoc on Systems

Computerworld - A faulty antivirus software update distributed by McAfee Inc. this month mistakenly identified hundreds of legitimate programs as a Windows virus -- a mix-up that led some unsuspecting corporate users to accidentally delete data from affected computers.

The update, released by McAfee on March 10, was designed to protect systems against the W95/CTX virus. But because of a programming error, the update also incorrectly identified, renamed and quarantined hundreds of legitimate executables, including popular ones such as excel.exe, lsetup.exe, reg.exe, shutdown.exe and uninstall.exe.

Santa Clara, Calif.-based McAfee replaced the flawed update with a new patch five hours after the first release. But for customers that had configured their antivirus programs to automatically delete bad files, the error resulted in the loss of hundreds or, in some cases, thousands of files, said Johannes Ullrich, chief research officer at the SANS Institute in Bethesda, Md.

"A lot depended on how you had McAfee configured on your system," Ullrich said. "If you had it configured to basically quarantine bad files, you were OK, because in this case it wasn't too hard to recover the quarantined files. But if you had it delete them, then [recovering the lost files] became a lot harder."

SANS received reports from "dozens" of companies reporting incorrectly quarantined or deleted files, he added.

Joe Telafici, director of operations at McAfee's virus-research unit, said the problem was the result of "a subtle logic flaw." The error resulted in at least 290 executable files being incorrectly identified as the targeted virus, he said.

"We are looking at a relatively small percentage of our customer base" that was affected, Telafici said. "But it is a large problem for those who were impacted."

McAfee's antivirus software for home users and small businesses includes a feature that can automatically restore quarantined files. Through its support organization, McAfee has begun offering a similar tool to corporate users, Telafici said. The tool also can be downloaded online.

McAfee is working on another tool that potentially could help companies restore some of the files that were deleted, Telafici said.