http://www.zdnet.com/sophos-update-bug-cripples-businesses-customers-affected-7000004646/
Sophos update bug cripples businesses; customers affected
Summary: Sophos' antivirus update bug may have overloaded systems administrators email inboxes, but it also had a knock-on effect for businesses and end-consumers around the globe.
Sophos antivirus software recognized a malware definition update as malware. The update files were detected as SSH/Updater-B malware by the Sophos software, which forced crucial update and core antimalware files into quarantine, resulting in the software grinding to a halt. Alert emails were sent en masse to administrators which required manual intervention on each and every machine, according to reports.