A bad malware signature caused Sophos antivirus products to detect a critical Windows file as malicious on Sunday. The false positive detection flagged winlogon, an important component of the Windows Login subsystem, as a Trojan program called Troj/FarFli-CT. Sophos issued an update to fix the problem within a few hours and said that the issue only affected a specific 32-bit version of Windows 7 SP1 and not Windows XP, Vista, 8 or 10. Users who encountered the black screen will have to reboot in Safe Mode and then boot into the OS normally.”]