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Here’s how to fix Windows Defender error 0x8000404

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Updated onOctober 4, 2023

updated onOctober 4, 2023

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UpdatingWindows Defendercan sometimes be quite a tricky task. There are various errors that can block the update process, but fortunately, most of them can be fixed using quick workarounds.

Error code 0x8000404 is one of the most frequent errors encountered byWindows Defender users, andappearswhen the definition updates can’t be installed.

I have tried three times to install the Virus & Spyware updates, the defination updates couldn’t be installed, the error code 0x8000404 – what do I have to do?

There are several possible causes for this error: another security program creates conflicts and blocksWindows Defender updates, some system files are corrupt or missing, the Internet connection in unstable, and more.

Fix Windows Defender error 0x8000404

Fix – Error 0x8000404 in Windows Defender

Solution 1 – Disable third-party antivirus

As we already know that Windows Defender is a part of the system, so installing a third-party antivirus can lead to certain interferences. In that manner, it’s advisable to disable a third-party antivirus in order to make Windows Defender work again.

However, you might consider changing your antivirus for a more efficient solution, so we recommend picking thebest antivirus tools with high detection rates.

Solution 2 – Make sure the Windows Defender service is running

For Windows Defender to run properly, you need its service to run properly. Obviously, if the service doesn’t work, neither will Windows Defender. In that manner, let’s go and check if the Windows Defender service runs properly, and re-enable it if not. Here’s how to do that:

Solution 3 – Make sure Windows Defender is running

Even if the service is running properly, the firewall itself could be disabled. Now, it should be enabled by default, but let’s check just in case. Here’s how to do that:

Solution 4 – Check for updates

As Windows Defender is part of the system, Microsoft releases updates for it through Windows Update. So, if there’s something broken inside Windows Defender, go on and check for updates. Maybe Microsoft has an ‘automatic’ solution.

To check for updates, simply go toSettings>Updates & Security, and check for updates.

Solution 5 – Remove latest updates

Just like installing a simple update can resolve the whole problem, it can also cause it in the first place. It’s actually a common sight that some cumulative update actually breaks something inside the system, and it could easily be Windows Defender. So, if you suspect the latest update you installed could have caused the problem, go on and delete that update.

If you’re not sure how to delete updates in Windows 10, just follow these instructions:

Solution 6 – Run the SFC scan

The SFC scan is a universal troubleshooting tool that can be used for fixing all sorts of issues in Windows 10. So, it might be helpful in this case, as well.

Follow these steps to run the SFC scan in Windows 10:

Solution 7 – Check the environment variables

Environment variables are a useful feature used by your system to access certain directories. However, sometimes users or perhaps a third-party application can change the environment variables and cause issues with Windows Defender.

To fix your environment variables manually do the following:

That’s about it. If you’ve come across other workarounds to fix Windows Defender error 0x8000404, list the troubleshooting steps in the comment section below.

More about the topics:Windows Defender issues

Madalina Dinita

Networking & Security Specialist

Madalina has been a Windows fan ever since she got her hands on her first Windows XP computer.

She is interested in all things technology, especially emerging technologies – AI and DNA computing in particular.

Prior to joining the WindowsReport team, she worked in the corporate world for a number of years.

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Madalina Dinita

Networking & Security Specialist

Madalina is a Windows fan since forever, especially interested in AI, emerging technologies, privacy, and security.