Windows Defender high CPU when idle

Solution 1:

Disabling \Microsoft\Windows Defender\MpIdleTask in the task scheduler will prevent autoscans when your computer is idle.

Solution 2:

1. Go to search on the charms bar.
2. Lookup Windows Defender.
3. Click on the settings tab.
4. Click on real time protection and uncheck "Turn on real time protection".

Or if you want to turn it off completely go to Administrator and uncheck "Turn on Windows Defender"

Solution 3:

You can add Windows Defender to the exclusion list for RT checks. It seems that it scans itself whenever it runs.

(Windows 8.1) Go to Control Panel > Windows Defender, click on the 'Settings' tab, browse to C:\Program Files\Windows Defender and select MsMpEng.exe, Hit 'Add' and 'Save changes' and that should help quite a lot.

It should be noted that now your computer will be vulnerable to any exploit that uses that file, but that beats being vulnerable to any infected file should you turn it off or exclude your entire C:\ drive as somebody else suggests.