A defective anti-virus update (4715 DAT) issued by McAfee on Friday falsely identified some Microsoft Office and Windows systems files as infectious - as a result placing them under quarantine, or even outright deleting them if a user had altered the default setting, reports the Register. The result was chaos: The antivirus program destroyed Microsoft Excel files, Adobe Update Manager components, Macromedia Flash Player, the Google Toolbar, and other files on numerous computer systems.

McAfee has released a new update along with a tool designed to recover legitimate system and application files from quarantine, but users are faced with the prospect of finding and restoring deleted files, writes PC Pro.

McAfee wouldn't say how many users were affected by the faulty software, which included VirusScan Enterprise 7.1 and above, Managed VirusScan 3.5 and 4.0 Beta, VirusScan Online 10, LinuxShield and VirusScan 7.03.