Wonky Windows 10 update breaks antivirus protection — here's the fix

What you need to know

• Several people are having issues with Windows Defender following a recent update.
• Security Intelligence 1.313.1638.0 seems to cause the issue.
• The only way to fix the issue right now seems to be performing a System Restore.

Updated April 17, 2020: You can now fix the issue by updating Windows Defender. We've added the steps to do so at the bottom of the article.

Another Windows Update is causing issues for people. This time, the bug prevents people from scanning their System using Windows Defender. Windows Latest reported the issue first, including its root cause. While some people are pointing to the update that brought Windows 10 KB4549951, the issue seems to actually be caused by Security Intelligence 1.313.1638.0,, which shipped earlier today.

People online have reported the issue (opens in new tab) and several people reached out to Windows Latest as well.

When trying to run a security scan, people see an error message that reads, "The threat service has stopped. Restart it now." Another error message that appears states, "Unexpected error. Sorry, we ran into a problem. Please try again." The bug prevents Full and Quick virus scans from running in Windows Defender.

Windows Latest reports that a Microsoft support team staff member confirmed that Microsoft is aware of the issue.

Tom's Hardware reports that you can now fix the issue by updating Windows Defender. The latest updating brings version 1.313.168.0. Here are the steps to update it.

1. Open Windows Search (You can do this by pressing Windows key + 'S').
2. Type Security.
3. Selecct Windows Security.
4. Click Virus & threat protection. Note: You may have to click the hamburger menu to see Virus & threat protection.
5. Click Check for updates (blue text).
6. Click Check for updates (within the box).