I turn on my PC and that happened, Kaspersky is on patch J, no changes and this never happened before.
I noticed by right-clicking a file and saw Windows Defender file scan on there.
Anti-malware service executable on task manager is running too.
Clean uninstall Kaspersky and reinstall lastest version .
It has happened to me too with Comodo Internet Security. Sometimes the AV can't register in Windows Security Center (even if it's running well) and Windows Defender re-activates.