Legitimate Websites Blocked Due to Buggy avast! Definitions Update

Avast! antivirus users experienced serious problems last night when the program began detecting infections on nearly all websites due to a bad definitions update.

According to Ondrej Vlcek, AVAST Software's chief technology officer, the problem was with the 110411-1 definitions update and affected websites containing scripts in a certain format.

"Our virus lab staff discovered the problem quickly after releasing the bad update and immediately started working on a fix.

"The fix was released about 45 minutes after the problematic update and has version number 110411-2," Mr. Vlcek wrote on the company's blog.

Triggering an update procedure from the antivirus program should have theoretically resolved the problem, but according to reports, things didn't go smoothly for everyone.

That's because after seeing the warnings, some people restarted their computers and initiated a so-called boot-time scan.

This scan, which takes place before Windows loads, detected infections in local html and javascript files and moved them to the virus chest (quarantine).

Some people were able restore them after installing the new definition update, but others uninstalled avast! after the boot-time scan didn't resolve the problem, leading to their permanent loss.

In addition, due to the sheer number of people looking for help, the company's forum which normally serves as primary method of assistance, became unreachable.

Suffice to say that a lot of people were upset over the incident, but that's the price to pay when your product has over 120 million active users and you do a mistake.

However, it's worth noting that avast! is not the only antivirus company to have experienced a false positive. Almost all AV vendors have gone through this at one point or another.

In fact, this wasn't even among the worst ones. In the past, products from other companies have deleted critical system files as a result of bad definitions, leaving hundreds of thousands of computers crippled or even unable to boot into the operating system at all.