The SANS Internet Storm Centre reported the problem, saying that an overnight update to CA's eTrust Antivirus signatures had caused the software to flag a security-related process in Windows as malicious. The faulty update caused some Windows 2003 servers to crash and become unusable, SANS says. The SANS note on this issue can be found here: http://isc.sans.org/diary.php?storyid=1665&rss

The problem was that eTrust Antivirus was mistakenly flagging the Windows Lsass.exe process, says Bob Gordon, a CA spokesman. "CA quickly discovered and fixed an issue which temporarily caused some customers to detect a problem in their Lsass.exe files," he adds.

According to Gordon, it took CA less than seven hours to fix the mix-up. The problem was introduced in the 30.3.3054 update, released at 2:53am Eastern Standard Time (EST) and fixed in the 30.3.3056 update, which was issued at 9:34am EST. CA's latest updates can be found here: SignDownload.aspx?CID=49737

The Lsass.exe process is part of Windows' security mechanism. So users who had set their eTrust Antivirus to automatically remove malicious software may have found that their systems crashed and were unable to boot up Windows once Lsass.exe was removed.

CA's guidance for users who have been experiencing crashes as a result of the buggy update can be found here: SignDownload.aspx?CID=49737

Anti-virus software like CA's uses digital fingerprints, called signatures, to identify malicious software. In this case, eTrust Antivirus apparently mistook Lsass.exe for the Win32/Lassrv.B virus.

It is not unheard of for signature files to mistakenly identify legitimate software as malware, but it is remarkable that CA's software made the mistake with a well-known Windows component, says Johannes Ullrich, chief research officer at SANS. CA should have been able to detect the problem in its quality-assurance testing, he adds.

The mix-up apparently did not disrupt a large number of users, but it still reflects poorly on vendors like CA, Ullrich says. "It is another loss in trust toward the anti-virus business," he adds. "It tells you that the anti-virus vendors do not do the testing."