The company acknowledged the issue in a , posted Saturday. "Due to a recent update it is possible that BitDefender detects several Windows and BitDefender files as infected with Trojan.FakeAlert.5," the company said.

The acknowledgement came after BitDefender users had logged hundreds of posts on the topic. Some complained of being unable to reboot their systems.

"EVERY file that is trying to run is getting quarantined," one user, identified as lhmathys, reported. "Windows Explorer and even Bitdefender update itself is being quarantined. Someone really screwed this one up."

"We are in a really terrible position now," , identified as ufitec. "We have 150 business clients and most of the pcs [on] which BitDefender thinks everything is virus does not boot any more!!!!"

In its note on the issue, posted around 4 pm Pacific Time, the company said it had issued a fix for the problem and offered instructions on how to repair the damage, saying that customers should remove files from quarantine and reboot.