FIX: Windows Defender scan issues on Windows 10

Ivan Jenic
by Ivan Jenic
Troubleshooting Expert
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  • Windows Defender is a powerful built-in tool designed to shield your PC against all kinds of malicious programs that may lurk around the corners of the web.
  • However, even the most performant tools get stuck every now and then and the Defender makes no exception. Here's how to solve its scan issues.
  • Get your hands on more useful information from our Windows Defender Guides.
  • Keen on expanding your horizons? Check our Windows 10 Troubleshooting Hub as well.
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It seems that after Windows Defender starts making a specific update to its database it will start having freezing issues or it will simply fail to start properly in Windows 10.

We have found a solution to this issue and it is as simple as it can get so you only have to follow the guidelines below in the order they are described and fix your Windows Defender in the Windows 10 operating system.

In most of the cases, the error message appears whenever you try to do a custom scan or a full scan on all your hard drives and it will most likely give you the pop-up message Windows Defender couldn’t scan your PC. This program service has stopped followed by the error code 0x800106ba.

So in the tutorial below, we will be doing a restore settings action back to where your Windows Defender did not have this issue and also a few additional checks to the system to make sure it is from the Windows Defender and not from the operating system itself.

How can I fix Windows Defender problems in Windows 10?

Windows Defender is a solid security application that can protect your PC from various threats. However, certain issues can appear with this tool, and speaking of issues, users reported the following problems:

  • Windows Defender not working Windows 10 – If you’re having problems with Windows Defender, the issue might be related to your Windows. To fix the problem, be sure to install the latest updates and check if that solves the problem.
  • Windows Defender quick scan stuck – Sometimes your Windows Defender can get stuck while scanning. To fix this problem, be sure to repair any corrupted files that you might have on your hard drive.
  • Windows Defender quick scan not working – This can be an annoying issue, but we already covered this topic in our Windows Defender won’t do a quick scan article, so be sure to check it out for more information.
  • Windows Defender your PC couldn’t be scanned – This is another problem that can occur with Windows Defender. However, you should be able to fix it by using one of our solutions.

1) Use Command Prompt

According to users, you might be able to fix problems with Windows Defender simply by using Command Prompt. To do that, follow these steps:

  1. Start Command Prompt as administrator.
  2. In the Command Prompt, you will need to write the following command:
    C:Program\Files\WindowsDefender\MpCmdRun.exe–removedefinitions

    Now press Enter to run the command.

  3. Once the command is executed, close Command Prompt and restart your PC.

Note: A very important thing to keep in mind is that you should not do the Windows Defender update again. If you want to do an update on the Windows Defender application make sure to check if Microsoft has fixed this issue.

If Windows Defender won’t turn on at all in Windows 10, here’s what you need to do.


2) Run System Restore

IMPORTANT: Before attempting this step make a backup copy of your files and folders that you will need because there is a possibility that after you do the system restore the files and folders might delete.

Another way to fix this problem is to use System Restore. This is a useful feature that can easily fix many problems on your PC. To use System Restore, you need to do the following:

  1. Press Windows Key + S and enter system restore. Choose Create a restore point from the menu.
    Windows Defender quick scan stuck
  2. System Properties window will now appear. Now click System Restore button.
    Windows Defender quick scan not working
  3. When System Restore window opens, click Next.
    Windows Defender your PC couldn't be scanned
  4. If available, check Show more restore points. Select the desired restore point from the menu and click Next.
    Windows Defender not working Windows 10
  5. Now follow the instructions on the screen to complete the restoration process.

Once your PC is restored, check if the problem still persists.


3) Check your exclusions

Many users reported certain problems while using Windows Defender. According to them, the issue was by exclusions. Sometimes malicious applications can add certain files or directories causing this problem to appear.

In fact, several users reported that their entire C drive was added to the exclusion list without their knowledge. This caused the problem with Windows Defender, but you can easily fix this issue simply by removing your exclusions. To do that, you need to follow these steps:

  1. Press Windows Key + I to open the Settings app.
  2. Now navigate to Update & security section.
    Windows Defender quick scan not working
  3. From the menu on the left choose Windows Defender. In the right pane, select Open Windows Defender Security Center.
    Windows Defender your PC couldn't be scanned
  4. Windows Defender Security Center will now appear. Click on Virus & threat protection.
    Windows Defender not working Windows 10
  5. Now select Virus & threat protection settings.
    Windows Defender quick scan stuck
  6. Scroll down to the Exclusions section and click on Add or remove exclusions.
    Windows Defender quick scan not working
  7. Now you should see all available exclusions. Select the exclusion and click the Remove button.
    Windows Defender not working Windows 10

Remove all exclusions from Windows Defender and check if that solves the problem.


4) Perform SFC, DISM and chkdsk scans

According to users, sometimes problems with Windows Defender can occur due to corrupted system files. To fix the issue, it’s recommended to perform an SFC scan. To do that, follow these steps:

  1. Press Windows Key + X to open Win + X menu. Select Command Prompt (Admin) from the list. If Command Prompt isn’t available, you can also use PowerShell (Admin).
    Windows Defender quick scan stuck
  2. When Command Prompt starts, enter sfc /scannow and press Enter.
    Windows Defender quick scan not working
  3. SFC scan will now start. Wait for the scan to finish. Keep in mind that this scan can take up to 15 minutes.

Once the scan is finished, check if the problem still persists. If you were unable to run SFC scan or if the problem still persists, you might want to try using DISM scan instead. To do that, follow these steps:

  1. Start Command Prompt as administrator.
  2. When Command Prompt opens, enter DISM /Online /Cleanup-Image /RestoreHealth and press Enter to run it.
    Windows Defender your PC couldn't be scanned
  3. DISM scan will now start. Keep in mind that this scan can take up to 20 minutes to complete, so don’t interrupt it.

Once the DISM scan is finished, check if the problem still persists. If the issue is still present or if you were unable to run SFC scan before, be sure to repeat the SFC scan again. After doing that, the problem should be completely resolved.

Several users are also recommending to use chkdsk scan. To do that, follow these steps:

  1. Start Command Prompt as administrator.
  2. Now enter chkdsk /f X:. Keep in mind that you need to replace X with the letter that represents your system partition. In most cases, that would be C. Press Enter to run the command.
    Windows Defender quick scan stuck
  3. If you decide to scan your C drive, you’ll need to schedule a scan and restart your PC. To do that, press Y in Command Prompt and restart your PC.
  4. Once your PC restarts, chkdsk scan will start automatically. Wait for the scan to complete. Depending on the size of your partition, the scan can take up to 20 minutes or more.

Once the scan is completed, check if the problem still persists.


5) Install the latest updates

If you’re having problems with Windows Defender, the issue might be related to your Windows. Certain bugs can appear once in a while and these bugs can interfere with Windows Defender.

By default, Windows 10 automatically downloads the missing updates, but sometimes you might miss an update. However, you can always check for updates by doing the following:

  1. Open the Settings app and navigate to Update & security section.
  2. Now click on Check for updates button.
    Windows Defender not working Windows 10

Windows will check for available updates and download them in the background. After installing the latest updates, check if the problem still persists.


6) Use a third-party antivirus

If you still can’t fix the problem with Windows Defender, you might want to consider switching to a third-party antivirus solution. We covered antivirus software in the past, and if you’re looking for a new antivirus application for your PC, we have to recommend PIA, CyberGhost, and BullGuard.

All these tools offer great features, so if you can’t fix your problem with Windows Defender, feel free to try any of these tools.


There you have it, 6 methods that will show you exactly what you need to do in order to fix your Windows Defender in the Windows 10 operating system.

You can also write to us in the comments section if you have any other additional issues or questions regarding this subject.

FAQ: Learn more about Windows Defender

  • How do I install Windows Defender on Windows 10?

Open the Control Panel-> System and Security and turn on Windows Defender. If you are unable to access the Control Panel, check out this guide.

  • Is Windows Defender enough to protect my PC?

Windows Defender has ranked high in performance tests. Nevertheless, you can always strengthen security by also installing a third-party antivirus.

  • How do I reset Windows Defender?

Open the Control Panel-> System and Security ->Windows Defender and select Restore defaults. You can also use the command netsh advfirewall reset in Command Prompt.

Editor’s Note: This post was originally published in March 2018 and has been since revamped and updated in March 2020 for freshness, accuracy, and comprehensiveness.

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