So it seems that with ever new major Windows 10 release Antivirus software gets broken. I had been running McAfee which I was forced to uninstall before upgrading. Intel/McAfee is vague about when a RS3 compatible version will be release, they just state "4th quarter 2017". I've also tried Bitdefender and it seems the firewall is broken under RS3 and blocks all IPV6 traffic and domain connectivity. So other than the built in Windows Defender, is anyone using an Antivirus product successfully with 16299.15?
As always it will need a moment for AV vendors to adapt. Build is in the wild for ~ week, and not even officially released to public.
Golden rule: before upgrading to the Fall build, uninstall your AV ! I tested Emsisoft Anti-Malware on RS3, worked fine.
KIS 2018 with experimental patch D working fine... You must go to Kaspersky forum beta section and follow up instructions.