Microsoft defender security locked my computer can't do anything

Slowride Pellechio 0 Reputation points
2026-08-28T21:41:14.43+00:00

I received error message saying Microsoft defender security center found infected files. It locked my computer can't do anything. the pointer is gone I can't do anything. Q&A says to download a fix it but I can't click anything. I shut down my computer and restarted. I went to settings and was looking for update & security then the error message popped up again. Need tech support

Microsoft Security | Microsoft Defender | Other
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  1. EmilyS_726 26,235 Reputation points Volunteer Moderator
    2026-08-29T21:09:13.34+00:00

    Hello

    Does this happen when you were browsing the web? It sounds like more an IT support to me.

    Can you please hold down Ctrl+Alt+Del, then launch Task Manager, and then end all browser items there to close it. That page is definitely scam, but as long as you didn't call the number and engage in any of the requested activities, your computer is not hacked. It is just a pop-up page that can have some audio effect (sometimes) and display in full screen mode, so it appears the computer is locked.

    Scammers use various methods to trigger these pop-ups. Pop-ups are a form of online advertising. They are often integrated into websites or applications through ad services. Many websites use third-party advertising services to display ads. Sometimes, these ad services might inadvertently allow scam ads to be displayed. This does not mean the website itself is malicious, but it indicates a lack of stringent ad vetting.

    You can read more about this type of support scam here: https://support.microsoft.com/windows/protect-yourself-from-tech-support-scams-2ebf91bd-f94c-2a8a-e541-f5c800d18435

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  2. Bence Weiszmann 1,390 Reputation points
    2026-08-29T20:37:18.6166667+00:00

    Dear @Slowride Pellechio

    Based on the behavior you described, this does not sound like a genuine Microsoft Defender notification. A message claiming that “Microsoft Defender Security Center found infected files,” locking the screen, and telling you to download a “fix” is typical of a technical support scam.

    Since you have already restarted the computer, I would not click the message, download anything it recommends, or call any phone number displayed in the alert.

    Once you can access Windows normally, open Windows Security --› Virus & threat protection --› Protection history and check whether Microsoft Defender has actually reported a threat. A genuine Defender detection should be visible there.

    I would also recommend running a Full Scan from Windows Security after making sure Windows and Defender security intelligence are up to date.

    If the warning appears again, especially immediately after opening a web browser, it may be coming from a malicious webpage or browser notification rather than Microsoft Defender. In that case, close the browser completely and avoid interacting with the warning.

    If you entered your Microsoft account password, or any other credentials, into a page associated with this warning, change those passwords immediately. If you reused the same password on other websites, change it there as well. It would also be a good idea to review your Microsoft account's recent sign-in activity for anything you do not recognize and enable or verify multifactor authentication.

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  3. AI answer

    2026-08-28T21:41:33.3+00:00

    This is most likely a browser-based tech support scam, not a real Microsoft Defender lock. Microsoft error and warning messages never include phone numbers.

    Try these steps in order:

    1. Do not call any phone number shown in the message and do not enter any information.
    2. Close the browser page that is showing the alert:
      • Press Ctrl+Alt+Del.
      • Open Task Manager.
      • End browser processes, or close all browser items.
    3. If the browser cannot be closed, restart the PC. The warning telling not to restart is part of the scare tactic.
    4. After restarting, run a malware scan:
      • Go to Start > Settings > Update & Security > Windows Security > Virus & threat protection.
      • Under Current threats, select Scan options.
      • Select Windows Defender Offline scan and then Scan now.
      • Important: save work first, because the PC will restart before the offline scan starts.
    5. If Microsoft Defender keeps finding the same threat after restart, avoid revisiting the same website or email that triggered it. Repeated detection can happen if the malware is being reinstalled or if the same malicious site is opened again.
    6. If scans report a threat was partially removed, run the Malicious Software Removal Tool:
      • Press Windows key + R.
      • Run %windir%\system32\mrt.exe.
      • Allow it to make changes if prompted, then follow the prompts to scan and clean the PC.
      • Restart the PC and install the latest updates.
    7. If Microsoft Defender is encountering scan or removal errors, run Windows Update and, if needed, manually install the latest protection updates.
    8. Do not run another real-time antivirus product at the same time as Microsoft Defender. Multiple real-time security products can cause problems.

    If the same alert appears only inside the browser again, end the browser task and avoid that site. If Windows Security continues detecting real threats or the system remains unstable, use recovery/reset options after backing up files. Resetting or reinstalling can cause data loss, so back up files first and restore from backups created before the infection if possible.

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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