The Webroot antivirus went berserk yesterday late afternoon, as it flagged core Windows system files as malicious, and even started moving some of the affected files into quarantine, trashing customer computers.

Antivirus software programs are designed to ignore Windows system files, as they are crucial to the operation of the Windows OS.

Webroot was flagging these files as a generic W32.Trojan.Gen trojan, but this wasn't the biggest problem. Once the antivirus started moving files around, computers started showing errors, and some crashed.

The company says their antivirus went haywire between 1 PM - 3 PM MST (7 PM - 9 PM UTC), the period when Webroot moved Windows files to quarantine. The issue was eventually fixed, but many customers were left with hundreds or thousands of files moved to quarantine.

Webroot also blocked traffic to Facebook

About the same time, the Webroot antivirus also started tagging Facebook as a phishing site, blocking access to the social network.

The antivirus should have blocked Twitter because users took to the micro-blogging platform to show their discontent and trash the company.

At the peak of irony, their customer PR started answering customer who had issues with Windows files trapped in Webroot's quarantine with a link to a presentation about ransomware.

Most issues are fixed now

Nonetheless, Webroot's technical team moved quickly and pushed a fix for the Facebook issue late last night, according to a post on the company's forum.

The company also provided a set of instructions that customers could follow to restore files and prevent the antivirus from re-detecting the same Windows files as W32.Trojan.Gen.

These instructions are only useful for home edition users. Webroot is still working on a solution for its business clients, where a more complex fix is needed.

Two months ago, a Webroot update caused problems and crashed computers for some of its clients.

UPDATE [April 26, 2017]: In a subsequent announcement, Webroot provided more details and released a repair utility for business clients.