How to Fix Windows Defender Glitch

John Lister's picture

The latest Windows 10 update blunder temporarily left some users without full use of the system's in-built antivirus / antimalware protection. Though enthusiasts quickly spotted a workaround, the problem has now been fixed with a Windows 10 update.

The initial problem wasn't actually a system update to Windows 10 itself that caused the issue, but rather an antivirus definition update file for Windows Defender. Essentially, a "definition update" contains details of the latest known threats that the tool can immediately deal with.

For some users, the problem only arose when running a full scan of the computer, which stopped midway through and displayed messages such as "'Unexpected error. Sorry, we ran into a problem. Please try again."

For other users, Windows itself spotted something was amiss and flagged up the problem in a system tray message as something that needed addressing.

Double Dot Defect

People who investigated the problem found that for some reason Windows Defender was "glitching out" whenever it encountered a file that included two consecutive periods in the filename. This is in contrast to 99% of all files that contain a single dot found between the name of the file and the extension (such as .doc) that shows what type of program it uses to load the file. (Source:

That led to unofficial advice to search through the file system, spot such files, and remove one of the dots from the filename. While this appeared to work, it's a somewhat clunky task and could cause knock-on problems given that two consecutive periods is normally perfectly valid in a filename.

Update Fixed By Update

Fortunately Microsoft quickly fixed the problem with a fresh update. This may well have automatically installed, but users can make certain by opening the Windows Security app, either through the settings menus, or by clicking on the Start menu and searching for "Windows Security". (Source:

Once the apps open, users can click on "Virus and threat protection", scroll down to "Virus and threat protection updates", then click on "Check for updates."

What's Your Opinion?

Had you encountered this problem? Are you satisfied Microsoft tackled it quickly enough? Would such glitches deter you from relying on Windows Defender?

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