Security Policy Errors

How to Fix Windows Defender Threat Service Has Stopped Error

Muhammad Talha Oct 9, 2026 869 views

Question details

The user is attempting to restore their system's security protection after encountering an error where the Windows Defender threat service stops running unexpectedly.

How to Fix the Windows Defender Threat Service Has Stopped Error

Product: Microsoft Windows Defender
Device & OS: Windows
Scenario: Trying to open Windows Security to perform a scan or ensure real-time protection is active.
Observed behavior: Windows Security displays an error message stating that the threat service has stopped. The service refuses to start automatically, leaving the system potentially unprotected.

Before you start

Ensure you are logged into an account with Administrator privileges, as elevated permissions are required to modify system accounts, uninstall software, and execute PowerShell commands. Close all background applications and Office programs before proceeding.

Solution 1Recommended

Disconnect Conflicting Work or School Accounts

Administrative policies from connected work or school accounts can override local security settings and force Windows Defender services to stop.

Organizations often apply group policies that manage how security features behave on connected devices. Disconnecting these accounts removes the restriction and allows Defender to operate normally.

Open Windows Settings

Click on the Start menu and select the 'Settings' gear icon, or press the Windows key + I on your keyboard.

Navigate to Access Work or School

Click on 'Accounts' from the main settings menu, then select 'Access work or school' from the left-hand sidebar.

Disconnect the Account

Click on any connected work or school accounts that are not strictly necessary for your personal use, and select the 'Disconnect' button.

Restart Your Computer

Restart Windows to apply the changes and open Windows Security to verify that the threat service is running again.

Disconnect Conflicting Work or School Accounts

Account Sync Caution: Disconnecting a work or school account will remove your device from the organization's management network, which may temporarily prevent you from accessing enterprise emails or shared files.

Solution 2

Uninstall Conflicting Third-Party Antivirus Software

Third-party antivirus programs often disable Windows Defender automatically to prevent software conflicts and system instability.

Solution 3

Reset Windows Defender via PowerShell

If Defender components are damaged, running a reset command through an elevated PowerShell session can restore its default functionality.

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Frequently Asked Questions

Why does Windows Defender say the threat service has stopped?

This error usually occurs when another third-party antivirus program is actively running and takes over security duties, or when a connected work or school account applies administrative policies that intentionally disable Windows Defender services.

Will resetting Windows Defender using PowerShell delete my personal files?

No, resetting Windows Defender via PowerShell using the ResetPlatform command only restores the security application's configuration files to their default states. It does not affect your documents, photos, or other personal data.

How do I start Windows Defender in Safe Mode for troubleshooting?

To enter Safe Mode, hold the Shift key while selecting 'Restart' from the Windows Start menu. Then, navigate to Troubleshoot > Advanced options > Startup Settings > Restart, and press F4 or F5 to boot into Safe Mode, where you can safely run diagnostics.

What should I do if the PowerShell reset command fails?

If the built-in reset command fails, ensure you are running PowerShell as an Administrator. Avoid manually modifying protected system files or deleting registry keys. If the issue persists, contact official Microsoft Support for advanced diagnostics.

Microsoft Office Security Issues