How to Turn Off Windows Defender in Windows 10 - farhansadik/windows-machine-backup GitHub Wiki

Turn of real time protection
Open regedit as admin
Go to Microsoft Defender's location in the register. You'll do this by expanding each of the necessary folders in the left-hand section of Registry Editor as follows:
- Expand the "HKEY_LOCAL_MACHINE" folder by double-clicking it (skip this step if the folder is already expanded).
- Expand the "SOFTWARE" folder.
- Scroll down and expand the "Policies" folder.
- Expand the "Microsoft" folder.
- Click once the "Windows Defender" folder.
Create a new DWORD (32-bit) Value. Enter "DisableAntiSpyware" as the file name. When the DWORD file appears, type in DisableAntiSpyware and then press ENter.
Open the "DisableAntiSpyware" DWORD file. Double-click it to do so. A pop-up window will open. Replace the "Value data" number with 1. This essentially turns on the DWORD value.
Then Just Restart PC!

Re-enable Microsoft Defender when needed

If you decide that you want to re-enable Microsoft Defender in the future, do the following:

Go back to the Windows Defender folder in Registry Editor.
Click once the "Windows Defender" folder.
Open the "DisableAntiSpyware" value by double-clicking it.
Change the "Value data" from 1 to 0.
Click OK, then restart your computer.
Delete the "DisableAntiSpyware" value if you don't want it to be available later.