A dodgy update from BitDefender on Saturday bricked Win 64-Bit systems after it was applied.

Rogue signature updates meant that multiple Windows and BullGuard files were falsely flagged as infected with a Trojan (now identified as Trojan-FakeAlert-5) and quarantined. Affected systems were subsequently left with applications that wouldn't work on boxes that were incapable of successfully rebooting.

The ropey update was available for around three and half hours before it was pulled. BitDefender has apologised for the snafu and issued advice on restoring borked systems.

Customers of anti-spyware and spam filtering firm firm BullGuard, which uses BitDefender's anti-virus engine, were also similarly affected. BullGuard also apologised for the problem and gave a renewed vote of confidence in the effectiveness of BitDefender's technology in a blog posting.

Misfiring updates are a well known Achilles' Heel for anti-virus scanners. The problem of false alerts is becoming more common even as systems improve because of the increased number of malware threats, estimated at 50,000 a day.

The problems with the BitDefender update are more serious than the norm because system files were falsely detected as malign, resulting in unstable and unusable systems. ®