Windows Defender Security Has Disabled Your Computer

John Yasem 20 Reputation points
2026-10-16T19:33:15.3233333+00:00

While attempting to login to Facebook a browser tab appeared stating "Windows Defender Security Has Disabled Your Computer". The instructions stated "Contact Microsoft Windows support at 1(888)850-2002. The person at that number directed me to type in "www.ultraviewer.net" in the run command window. This took me to that site where he wanted me to download the app so he could view my computer and clear up the problem. Suspicious, I hung up and did not download anything. I immediately search for MS support to check it's validity.

Windows for home | Windows 11 | Security and privacy
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Answer accepted by question author
Erland Sommarskog 138.1K Reputation points MVP Volunteer Moderator
2026-10-16T21:34:59.24+00:00

Good call to hung up!

That browser tab came from a malicious ad (that Facebook should remove) and has nothing to do with your computer. Microsoft would never produce such a popup. If you had downloaded that app that would have been very bad for you computer. (And possibly also for your financials.)

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