Microsoft has just broken Windows 10’s antivirus protection – apply this fix straight away

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Update: Microsoft has now fixed this issue. Users were reporting that Windows Defender was crashing when running a full scan. It appears the issue was caused when Windows Defender encountered a file with a name with two periods (..) in it. Microsoft has now released a new Security Intelligence Update for Windows Defender that fixes this issue. The update should install automatically, but you can also manually install it by clicking 'Check for updates' in the Windows Security app.

Original story follows...

Microsoft has released yet another faulty update, and this time it appears to be causing some serious issues with Windows Defender, the built-in antivirus software that comes with Windows 10.

As Windows Latest reports, 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.


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.

Check out our guide on how to use System Restore for more information.

Matt Hanson
Managing Editor, Core Tech

Matt is TechRadar's Managing Editor for Core Tech, looking after computing and mobile technology. Having written for a number of publications such as PC Plus, PC Format, T3 and Linux Format, there's no aspect of technology that Matt isn't passionate about, especially computing and PC gaming. Ever since he got an Amiga A500+ for Christmas in 1991, he's loved using (and playing on) computers, and will talk endlessly about how The Secret of Monkey Island is the best game ever made.