Microsoft claims that Windows 11's built-in security tool is enough for most PC users, but that's only the case if the tool works. An issue affecting some PCs prevents security scans from being completed, leaving systems potentially vulnerable.
The problem was flagged on Reddit by user Huynh_Jovi. Several users in that thread have had issues running scans with Microsoft Defender. Both Full Scan and Quick Scan appear to be affected.
Pinned at the top of that thread is a comment by a moderator that gathers together key information on the situation.
"It appears Microsoft released a bad update to Windows Defender, causing it to crash a few seconds after attempting to perform a Full Scan or Quick Scan," reads the comment by user goretsky. They continue, stating, "Offline scans reportedly stop at around 90-93% of completion." The latest version of the Microsoft Safety Scanner is reportedly affected as well.
The exact cause of the issue has not been determined, though there are several suggested causes. The issue seems to be related to a Microsoft Security Intelligence update. Performing an upgrade to Security Intelligence Update v1.457.236.0 resolves the issue, according to Reddit users Schoonie84 and Master_Pie1940.
You don't need to hunt down that update manually. If you check for updates in the Windows Security app or through Windows Update, the latest version should appear.
There's a chance the issue appeared after Microsoft attempted to mitigate ShieldBreak, a zero-day vulnerability disclosed shortly after August's Patch Tuesday update.
Versions v1.1.26070.7 and v1.1.26080.2 of Defender are said to be affected by the issue when used with any of the following Microsoft Security Intelligence Update versions:
- 1.457.222.0
- 1.457.225.0
- 1.457.226.0
- 1.457.227.0
- 1.457.230.0
Restoring to an older Microsoft Security Intelligence update also reportedly fixes the issue, adding weight to the theory about the cause of the problem.
Commentfrom r/antivirus
Many users have spent hours trying to address the issue. At the time of publication, there has not been official word on the problem from Microsoft, so the work of the Reddit users taking a closer look is appreciated.
Performing regular scans is an important step in securing a PC. Hopefully Microsoft can resolve the issue quickly and get word out to affected users.
In the meantime, affected users can still scan a specific folder or drive by right-clicking and selecting "Scan with Microsoft Defender."
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