AVG flags Windows file as Trojan, cripples systems

(TheForceField.Net ) November 11, 2008 –  AVG issued an update for its populare anti-virus scanner November 9 that tagged a critical file in the Windows operating system as malware and deleted it, crippling an unknown number of systems.

A error in a virus definition update issued Sunday caused a false positive during a scan that indicated the Windows system file user32.dll was infected with a trojan called Generic9.TBN and deleted the file. Once the file was removed, users could not boot into Windows. Windows XP running AVG versions 7.5 and 8.0 were affected.

The solution was to boot to the Recovery Console from a Windows CD and restore the file to repair Windows and perform a restore installation of AVG. The company acknowledged the issue in their forums and posted a repair procedure and a fix tool on its support site. 

AVG apologized for the snafu in a press release on PRNewswire. "AVG sincerely regrets the inconvenience users have experienced", the release stated. "We are working to remedy the problem and ensure that any other potential vulnerabilities are identified and eliminated before they can impact users."

Windows Vista was not reported to be affected by the issue.