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Unexpected Error in Windows Defender: How to Fix

In this guide, we will show you various methods to fix the Unexpected Error in Windows Defender. While there are a slew of antivirus software available in the market, however, for many, it is the built-in one that manages to checkmark most of the prerequisites. The Defender app in combination with Windows Firewall provides one of the most secure environments, without you needing to spend a dime! However, what you might need to spend is your valuable time on rectifying various issues that it gets bugged with at regular intervals.

Unexpected Error in Windows Defender

For example, the “Unexpected Error” is among the most common problems in Windows Defender. However, it is also among the most confusing ones as the error message doesn’t give out any clue whatsoever as to what could be the plausible reason behind this issue. But fret not. In this guide, we will make you aware of numerous methods that shall help you fix the aforementioned error with ease. So without further ado, let’s get started.

How to Fix Unexpected Error in Windows Defender

Unexpected Error in Windows Defender

It is recommended that you try out each of the below-mentioned workarounds and then see which one spells out success for you. So with that in mind, let’s get started.

FIX 1: Disable Third-Party Antivirus

First and foremost, if you have any third-party antivirus app installed, then you should consider disabling it right away. There have been many instances wherein these antivirus apps tend to conflict with the normal functioning of Defender. So open the installed antivirus app and look out for the setting to temporarily disable it.

Unexpected Error in Windows Defender

Once done, launch Windows Defender and check if the Unexpected Error has been fixed or not. If it has been fixed and you are interested in continuing with Dendefer, then we would suggest you keep that antivirus app disabled or just uninstall it from your PC [from the Control Panel].

FIX 2: Use Microsoft Safety Scanner

This official tool from Microsoft is used to scan and then remove the malware from your PC. So if the underlying issue is due to a malicious program, then it should be rectified via this scanner.

  1. To begin with, download the Microsoft Safety Scanner from the official site.
  2. Then launch its EXE file, select Full Scan, and hit Next.Unexpected Error in Windows Defender
  3. The tool will now scan for malware and would subsequently remove them.
  4. Once done, check if it fixes the Unexpected Error in Windows Defender.

FIX 3: Disable Windows Firewall

In rare instances, it has been noticed that the built-in Firewall application tends to act over-protective/aggressively and in turn ends up conflicting with the normal functioning of the PC. Therefore, you should consider disabling it and then check out the results. Here’s how it could be done:

  1. Head over to the Start menu, search Windows Defender Firewall, and open it.
  2. Then click on Turn On/off Windows Defender Firewall from the left menu bar.
    Unexpected Error in Windows Defender
  3. After that, select Turn off under both the Public and Private networks.
    Unexpected Error in Windows Defender
  4. Now, check if it fixes the Unexpected Error in Windows Defender.

FIX 4: Restart Windows Defender Services

If Defender’s background running services aren’t performing along the expected lines, then its repercussions will be faced with the app. Therefore, you should double-check all its associated services are working well and good. Here’s how:

  1. Open Services from the Start Menu and select Security Center.
  2. Then make sure that it is running. If it’s not, then hit the Start button.Unexpected Error in Windows Defender
  3. Likewise, verify the status of Windows Defender Antivirus Service and Windows Security Service.
  4. Once done, check if it fixes the Unexpected Error in Windows Defender.

FIX 5: Tweak DisableAntiSpyware Value

Tweaking the value of the DisableAntiSpyware registry file has spelled out success for some users as well. So take a registry backup beforehand and then follow the below instructions-

  1. Launch Registry Editor and head over to the below location
    Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender
  2. Then right-click on the Windows Defender folder and select New > DWORD (32-bit) Value.Unexpected Error in Windows Defender
  3. Name it DisableAntiSpyware and double-click to open it. Then type in 0 in Value Data.Unexpected Error in Windows Defender
  4. Finally, click OK and check if it fixes the Unexpected Error in Windows Defender.

FIX 6: Use Microsoft Defender Offline Scan

If none of the aforementioned methods managed to spell out success, then your last course of action should be to opt for the Offline Scan feature. Here’s how it could be done

  1. Open Windows Security from the Start Menu and click on Scan Options.
  2. Then select Microsoft Defender Offline Scan and hit Scan Now.Unexpected Error in Windows Defender
  3. Wait for the scan to complete [it will take some time to complete].
  4. Once done, verify if it fixes the underlying issue or not.

That’s it. These were the five different methods that shall help you fix the Unexpected Error in Windows Defender. If you have any queries concerning the aforementioned steps, do let us know in the comments. We will get back to you with a solution at the earliest.


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