Windows Defender high CPU when idle

ok, because I saw the RtlScrubMemory issue several time I asked Microsoft about it. This functions is used to test the installed RAM.

I saw it when the idle Maintenance kicks up and tries to optimize Windows. Disable the Idle Maintenance task in task scheduler to get rid of it.

Found the answer myself (more details here). Basically, it's as simple as setting the Group Policy called Monitor file and program activity on your computer to Disabled.

For users of Windows editions without gpedit.msc, a DWORD entry called DisableOnAccessProtection must be created under HKEY_LOCAL_MACHINE\Software\Microsoft\Windows Defender\Real-Time Protection and set to 1.

The name of this registry entry tells you exactly what "Monitor file and program activity" actually do: It scans files "On Access" (such as when Windows Explorer lists the contents of a directory). Nothing more.