Fix: Windows Defender error 577

By: Milan Stanojevic
7 minute read

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Windows Defender might not be the best antivirus software, but it’s the default antivirus tool that comes installed with Windows 10. This tool has its flaws and users reported error 577 with Windows Defender, so let’s see how to fix it.

Windows Defender error 577, how to fix it?

Windows Defender is a solid antivirus, but several users reported error 577 in Windows Defender. This error can be problematic, and speaking of this error, here are some similar issues that users reported:

  • Windows Defender this program is turned off – This message is closely related to error 577, and if you encounter it, be sure to enable Windows Defender using the Registry Editor.
  • Windows Defender turned off by group policy – Sometimes Windows Defender can be disabled from Group Policy. However, you can fix this problem simply by changing your group policy settings.
  • Windows Defender error 577 McAfee, Avast, Kaspersky – Third-party antivirus tools can often interfere with Windows Defender and lead to this error. Even if you don’t have a third-party antivirus installed, sometimes leftover files can interfere with Windows Defender and cause error 577.
  • Can’t start Windows Defender error 577 – Many users reported that they are unable to start Windows Defender due to this error. If that’s the case, try restarting Windows Defender services and check if that helps.
  • Windows Defender digital signature error 577 – This is another variation of this error, but if you encounter it, you should be able to fix it one of our solutions.

Solution 1 – Consider switching to a third-party antivirus software

Windows Defender is a solid antivirus tool, it offers great protection, comes built-in to Windows 10, and it’s completely free. Despite all these great features, issues with Windows Defender can occur, therefore you might want to consider switching to a third-party antivirus.

Although Windows Defender offers basic protection, it lacks certain features that other antivirus tools have, so if you want to avoid this error and get improved security, you might want to consider a third-party antivirus. There are many great tools, but the best one is Bitdefender (currently World’s Nr.1), so feel free to it out.

This tool offers a wide array of security features, and it’s fully compatible with Windows 10, so it won’t interfere with your applications or with your system in any way.


Solution 2 – Change your registry

According to users, you can fix this problem by changing few values in your registry. Before you start you need to know that modifying your registry can cause certain issues, therefore we strongly suggest to create a backup of your registry in case anything goes wrong. To edit your registry, follow these steps:

  1. Press Windows Key + R and enter regedit. Press Enter or click OK.
    Windows Defender turned off by group policy
  2. When Registry Editor opens, navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender key in the left pane.
  3. In right pane locate DisableAntiSpyware and DisableAntiVirus DWORD and change their values from 0 to 1. You can do that simply by double-clicking the entries and changing the Value data value.
  4. Click OK to save changes.
    Windows Defender this program is turned off
  5. Optional: Some users are suggesting to go to HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender key and change DisableAntiSpyware and DisableAntiVirus entries as well, so you might want to do that.
  6. Close Registry Editor.
  7. Go to C:\Program FilesWindows Defender and try to run MSASCui.exe.
    Windows Defender turned off by group policy

If you get an error message saying that you don’t have the necessary privileges, try performing Solution 4 fist and then try the entire process again. As we already mentioned, modifying the registry is an advanced procedure, so be extra cautious and follow the instructions carefully.

If you’re still having issues on your PC or you simply want to avoid them for the future, we recommend you to download this tool to fix various PC problems, such as registry errors, corrupted files,  file loss, malware and hardware failure.


Solution 3 – Completely remove third-party antivirus tools

Windows Defender doesn’t work with third-party antivirus programs, therefore it’s impossible to have another antivirus tool installed and run Windows Defender at the same time. In order to avoid this problem, you need to completely remove your antivirus tool.

Sometimes it’s not enough just to uninstall your antivirus, you have to remove all files and registry entries associated with your antivirus tool. You can do that manually, but that’s not the safest or the simplest processes, therefore we recommend that you download the cleanup tool for your antivirus software. Almost all antivirus companies have these tools available for download, so be sure to download this tool for your antivirus program.

Users reported that Avast, Norton and McAfee antivirus tools caused this problem, and after removing all files associated with your antivirus, the issue was completely resolved. In addition to your antivirus, tools such as SpyBot Search and Destroy, Comodo Antivirus, Constant Protection and IOBIT Malware Fighter can also cause this error, therefore be sure to remove these tools from your PC.


Solution 4 – Turn on Windows Defender from Notification Center

According to users, you can fix this problem simply by turning on Windows Defender from Notification Center. To that, go to Notification Center at the bottom right corner of the screen and you’ll see an alert with a little flag next to it. Click it and Windows Defender should turn itself on.


Solution 5 – Change the security permissions in your Registry

Sometimes this problem can occur due to your security permissions in the registry. To fix error 577, you need to change the security permissions of certain keys in the registry. Modifying the registry can cause problems with your system, therefore we advise you to create a registry backup before you start. To change the security permissions, follow these steps:

  1. Open Registry Editor.
  2. Go to the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender key in the right pane.
  3. Right-click this key and choose Permissions from the menu.
    Windows Defender error 577 McAfee
  4. Click the Advanced button.
    Can't start Windows Defender error 577
  5. Click the Add button.
    Windows Defender digital signature error 577
  6. Now click Select a principal.
    Windows Defender this program is turned off
  7. In the Enter the object name to select field enter your user name and click Check Names.
  8. If your user name is correct, click OK to save changes.
    Windows Defender turned off by group policy
  9. You’ll see your username in the Principal section. In Basic permissions section check Full Control and click OK to save changes.
    Windows Defender error 577 Avast
  10. Click Enable Inheritance button.
    Can't start Windows Defender error 577
  11. Click Apply and OK to save changes.

If you haven’t already, be sure to do all the steps from Solution 1.


Solution 6 – Restart Security Center and Windows Defender service

According to users, you can fix Windows Defender error 577 simply by restarting Security Center service. This error can appear after you remove your antivirus tool, and users reported this issue after removing McAfee LiveSafe tool. To restart Security Center service follow these steps:

  1. Press Windows Key + R and enter services.msc. Press Enter or click OK.
    Windows Defender error 577 McAfee
  2. Locate Security Center service, right-click it and choose Restart.
    Can't start Windows Defender error 577

Alternatively, you can restart this service simply by right-clicking the Security Center service and choosing Stop from the menu. After that, right-click the service again and choose Start from the menu.
Windows Defender this program is turned off

Some users claim that you can fix this problem by starting Windows Defender from Services. To do that, open Services window and locate Windows Defender. Right-click it and choose Start from the menu.

If the issue still persists, we also recommend you to download this tool  (100% safe and tested by us) to scan and fix various PC problems, such as file loss, malware and hardware failure.


Solution 7 – Create a new user account

Sometimes this error can appear because your user account is corrupted. If that’s the case, you need to create a new user account by following these steps:

  1. Press Windows Key + I to open the Settings app.
  2. Now navigate to the Accounts section.
    Windows Defender turned off by group policy
  3. Select Family & other people and click on Add someone else to this PC.
    Windows Defender error 577 Kaspersky
  4. Now click on I don’t have this person’s sign-in information.
    Can't start Windows Defender error 577
  5. You’ll be asked to enter your Microsoft credentials. Select Add a user without a Microsoft account.
    Windows Defender digital signature error 577
  6. Enter the desired name and click on Next to proceed.
    Windows Defender this program is turned off

Once you create a new user account, switch to it and check if the issue is resolved. If the problem doesn’t reappear, you’ll need to move your personal files to the new account and start using it instead of your main account. This isn’t the most practical solution, but several users reported that it worked for them, so feel free to try it out.

Windows Defender error 577 can be problematic, but you should be able to fix it by using one of our solutions. If you can’t fix this problem, you might want to consider using a third-party antivirus software instead.


Editor’s Note: This post was originally published in September 2016 and has been since completely revamped and updated for freshness, accuracy, and comprehensiveness.


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