Windows 10 Defender gets faulty update and its antivirus protection had broken

As Windows Latest reports (see 1), it appears that an automatic update, known as Security Intelligence 1.313.1638.0, which was only recently released by Microsoft, is causing Windows Defender to show error messages saying “Threat service has stopped. Restart now,” and “Unexpected error. Sorry, we ran into a problem. Please try again.”


Most worryingly of all, the issues appear to prevent users from being able to run Windows Defender scans to check Windows 10 for viruses and security problems.

Indefensible

Microsoft is having a rough time of late when it comes to pushing faulty updates, but this is one of the most concerning. Because Windows Defender is built into Windows 10, it’s used by a huge amount of people to keep their PCs safe when online.


If the update is causing Windows Defender to stop working, millions of PCs could be at risk.

Fix the issue

If you’re relying on Windows Defender to protect your PC, and you’re unable to get it to run, then you’ll be understandably keen to fix this issue as soon as possible.

It seems you can’t just uninstall the update to get it to work. However, Windows Latest reports that if you perform a System Restore to a date before you installed the update, that should fix the issue.

To do this, type ‘System Restore’ into the search box of the taskbar. Click ‘Create a restore point’, then in the window that appears, select ‘System Restore’.

Click 'Next', then choose a restore point from the list. There should be a Restore Point from a date earlier than April 16, which is when the update was released.

Before you click 'Next' to move on, it’s a good idea to click 'Scan for affected programs' to see what (if any) programs will not be installed if you use this restore point. Once you’ve done that, click 'Close', then 'Next', then 'Finish' to confirm you want to restore this particular point.


How to fix ‘Threat service has stopped. Restart now’ in Windows Defender

It appears that the problem is caused by files with two dots (..) in their name and the error will disappear if you rename or delete the files.

To fix ‘Threat service has stopped. Restart now’ error in Windows Defender, follow these steps

  • Open Event Viewer.
  • In Event Viewer, navigate to Applications and Services logs > Microsoft > Windows > Windows Defender > Operational.

Look there for error and you’ll find something like “crash exception code 0xc00000005 ” and it includes the name of the file with two dots. To resolve the issue, remove the extra dot or delete the file.

Once you’ve fixed the file, go to services and start Windows Defender and perform a quick scan. This should resolve the problem.

In a chat with Microsoft’s support team, one staff member told us that Microsoft is aware of the ongoing issue.

Microsoft could soon deliver the fix with another ‘Security Intelligence Update for Windows Defender Antivirus’, so you need to make sure you’ve not disabled Windows Updates.

References:

(1): support.microsoft.com/en-us/help/4549951/windows-10-update-kb4549951