A routine anti-virus update from Web security firm McAfee confused a valid Windows file with a virus on Wednesday, disrupting an unknown number of computers around the world.
The problem hit enterprises running Microsoft's Windows XP Service Pack 3 operating systems, according to reports, but it was not immediately clear how many machines had been affected.
The problems included computers which were continually rebooting after the update identified a valid Windows system file as malicious code.
The Internet Storm Center, an initiative of the SANS Technology Institute which monitors problems on the Internet, said that it had received up to 100 submissions about the problem.
"Some report about networks with thousands of down machines and organizations who had to shut down for business until this is fixed," the Internet Storm Center said.
"The affected systems will enter a reboot loop and lose all network access," the Internet Storm Center said in a blog post.
McAfee released an update which it said stopped the "false detection" and urged customers to download it.
A McAfee spokesman did not respond to a request for comment from AFP and a McAfee online support forum was unavailable, displaying a page which read: "The McAfee Community is experiencing unusually large traffic which may cause slow page loads. We apologize for any inconvenience this may cause."Reuse content