How to Turn On PUA Protection in Microsoft Defender

Meta description: Enable Defender protection against potentially unwanted apps before they clutter or weaken the PC, and Kudu can help review threats.

What Causes This?

Potentially Unwanted Application (PUA) protection in Microsoft Defender is often off by default on some Windows setups, or it may have been disabled during a system tweak, policy change, or third-party antivirus install. When it’s off, Windows is less likely to block adware, bundled installers, browser hijackers, and other low-risk but annoying software.

This usually becomes a problem after installing free apps from download sites, browser extensions, or software bundles that add unwanted extras without making it obvious.

Common Symptoms

• Pop-ups, ads, or unwanted browser redirects start appearing
• New apps or toolbars show up that you did not intentionally install
• Defender does not warn about suspicious bundled installers
• Search engine or homepage settings keep changing
• The PC feels more cluttered after installing “free” software

How to Fix It Manually

1. Open Windows Security

   • Click Start
   • Type Windows Security
   • Select Windows Security from the results

2. Go to App & browser control

   • In the left sidebar, click App & browser control
   • Look for a section called Reputation-based protection

3. Open Reputation-based protection settings

   • Click Reputation-based protection settings
   • Find the setting for Potentially unwanted app blocking

4. Turn on PUA protection

   • Switch Potentially unwanted app blocking to On
   • Enable both:
     • Block apps
     • Block downloads
   • This helps Defender stop suspicious apps before they install and warns you about risky downloads

5. If the option is missing, check for Windows updates

   • Press Windows + I to open Settings
   • Go to Windows Update
   • Click Check for updates
   • Install any pending updates, then restart your PC and check again

6. Make sure Microsoft Defender is active

   • In Windows Security, click Virus & threat protection
   • If another antivirus is installed, Defender’s settings may be limited or managed by that software
   • If you want Defender to handle PUA protection, remove or disable the third-party antivirus first

7. Use PowerShell if the setting still won’t turn on

   • Right-click Start and choose Windows Terminal (Admin) or PowerShell (Admin)
   • Enter this command and press Enter:

     Set-MpPreference -PUAProtection 1

   • Restart the PC after running the command

8. Run a quick scan

   • Open Windows Security
   • Go to Virus & threat protection
   • Click Quick scan
   • If Defender finds anything, review the results and remove or quarantine the items

If your PC is managed by a workplace or school, this setting may be controlled by Group Policy, and you may not be able to change it yourself.

Fix It Automatically with Kudu

Kudu can help you spot unwanted apps, bundled software, and security settings that leave your PC more exposed. If Defender’s PUA protection is off or your system already has clutter from suspicious installs, Kudu can review the problem areas and help clean them up faster.

Download Kudu Free →