How to Determine if Defender ATP (Windows Security) is Operating on Your PC Step 1 Click the search icon on the bottom left and search for Windows Security. Step 2 Click Open to open the Windows Security (Defender ATP) application. Step 3 Click Virus & Threat Protection from the left-side menu. Step 4 Click Manage settings under Virus & threat protection settings. Step 5 If the text says “This setting is managed by your administrator,” Windows Defender ATP is operating on your system. Last modified: September 25, 2020