Is it just me or does the CPU usage of Windows Defender ramp up to an absurd level when you leave your system idle? AFAIK, when your system is idle, Windows Defender will execute a number of tasks that range from scanning to updating itself. I literally could not go to sleep the other night because my fans would continuously start up every time I got back into bed. Eventually, I figured out it was msmpeng.exe, and the only way to stop it was to disable real-time protection in Windows Defender. Even disabling all of the related entries in Task Scheduler wouldn't stop it.