Sophos antivirus products detected winlogon.exe as malicious A bad malware signature caused Sophos antivirus products to detect a critical Windows file as malicious on Sunday, preventing some users from accessing their computers. The false positive detection flagged winlogon.exe, an important component of the Windows Login subsystem, as a Trojan program called Troj/FarFli-CT. Because the file was blocked, some users who attempted to log into their computers were greeted by a black screen. 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. “Based on current case volume and customer feedback, we believe the number of impacted systems to be minimal and confined to a small number of cases,” the company said in a support article. One Twitter user who was affected by the issue said that he highly doubts only a small number of customers were affected, while another one reported that he’s been on hold trying to reach Sophos Support by phone for over two hours. “An email would have been nice,” one user told Sophos via Twitter. “I cannot imagine the costly overtime $ and panicked IT staff like myself working on this.” Another user joked that this false positive actually removed some of his weekend. In many cases administrators will only need to clear the bogus alerts from the Sophos Enterprise Console, Sophos Central or Sophos Home by marking them as resolved or acknowledged, the company said. Users who encountered the black screen will have to reboot in Safe Mode, disable the Sophos Anti-Virus service from starting automatically and then boot into the OS normally. More detailed instructions are available in Sophos’ support document. Sophos is not the first antivirus company to issue a bad definition that affected users’ computers. To its credit, the company reacted promptly and fixed the issue in a timely manner during a weekend, but questions remain as to why in 2016 an antivirus program can still flag legitimate Windows system files as malicious. False positive detections used to be much more frequent years ago, but most antivirus companies have since built whitelists of known software to avoid such incidents. Windows files in particular should be a top priority for whitelisting because blocking or deleting them can leave a computer unusable. Related content analysis BGP: What is border gateway protocol, and how does it work? BGP is how the autonomous networks that make up the internet share routing information to find the best route for IP traffic. CISA describes BGP as 'the most important part of the internet you’ve probably never heard of.' By Keith Shaw May 17, 2024 11 mins Routers Internet Network Security feature Red Hat seeks to be the platform for enterprise AI By Maria Korolov May 17, 2024 12 mins Linux Network Management Software news FCC proposes BGP security measures Protecting the Border Gateway Protocol is as important as protecting the border. By Gyana Swain May 17, 2024 4 mins Regulation Network Security brandpost Sponsored by Zscaler 5 Must-haves for your next DSPM solution Elevating cloud security: Navigating the data storm with DSPM By Kalie Radsmikham, Sr. Director of Product Marketing, Cloud Security May 16, 2024 7 mins Cloud Computing PODCASTS VIDEOS RESOURCES EVENTS NEWSLETTERS Newsletter Promo Module Test Description for newsletter promo module. Please enter a valid email address Subscribe