Users of ESET antivirus software that have upgraded Windows 10 to the latest November update (Threshold 2 / Fall Update / build 1511) might find the software is uninstalled. Older versions of ESET Endpoint Antivirus, Endpoint Security, Nod32 Antivirus and Smart Security are not compatible with Windows 10. When systems running those versions are upgraded to Microsoft’s latest OS, the software is uninstalled and Windows 10 uses Windows Defender as antivirus product again.
As a reason older versions of ESET software are removed after the November update the company writes, “Microsoft has changed their rules for detection of compatible applications.”
In practice that means that Windows 10 didn’t trust the ESET software and decided to remove it.
ESET has released a fix and advises users to first install the latest version of their software before upgrading to Windows 10.