Windows Defender Group Policy
You can use the Windowsdefender.adm Group Policy template file to control the policy settings for Windows Defender when Windows Defender is installed on a computer that is running Microsoft Windows XP or a later operating system.
By default, the installation location of Windows Defender is the C:\Program Files\Windows Defender folder. The Group Policy administrative template file is put in the Windows Defender folder when you install Windows Defender. The file name of the Group Policy administrative template is Windowsdefender.adm.
For more information, see MS KB927367 entitled Description of the Windows Defender Group Policy administrative template settings