Avast update falsely flags good apps as malware

Czechoslovakia-based antivirus maker fixes security update that mistakenly identified good programs as a Trojan.

Elinor Mills Former Staff Writer

Elinor Mills covers Internet security and privacy. She joined CNET News in 2005 after working as a foreign correspondent for Reuters in Portugal and writing for The Industry Standard, the IDG News Service and the Associated Press.

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Elinor Mills

Dec. 4, 2009 11:04 a.m. PT

Czech Republic-based Avast issued an update late on Wednesday to its antivirus software that mistakenly flagged hundreds of innocent files as a Trojan. It fixed the situation five and a half hours later.

Falsely labeled as malware were programs from Adobe, Realtek, sound card drivers, and various media players, among others, according to a blog post on the Avast Support Center.

The errant update had been issued around 12:15 a.m. GMT. A new update was issued at 5:50 a.m. GMT that corrected the problem. Customers who did not use their computers between that time will most likely not be impacted, the company said.

The software was identifying the good files as the Win32:Delf-MZG Trojan, according to Avast.

Avast, based in Prague, did not respond to an e-mail late on Wednesday seeking comment.

False positives happen in the industry. In July, Computer Associates' antivirus software was falsely tagging a Windows XP system file as a virus, and last year AVG falsely identified a file from security provider ZoneAlarm as a virus.