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Microsoft pop-up scam: is that security warning real?

Editorially reviewed · Last updated September 8, 2026

Yes — this is a scam. Microsoft's error and warning messages never include a phone number — a pop-up that gives you one to call is always a scam.

Exhibit · Browser pop-up

windows-defender-alert[.]net/security
Windows Defender — Security Warning

** Access to this PC has been blocked ** Suspicious activity detected. Your passwords, browsing history and banking details are being stolen. Do not restart or shut down your computer. Call Microsoft Support now:

+1 (855) 555‑0164

Call Microsoft Support

Do not close this window · Error # 0x80070424

Illustrative browser pop-up · not an original screenshot

Other versions you might get: A full-screen browser lock, a loud alarm sound with a robotic voice, a fake “Windows Defender” or “Microsoft Support” chat window, or a call claiming to be from Microsoft about a virus or an expiring license. Whatever the wrapper, the ask is to call, install remote-access software, or pay for “support.”

What to do right now

  1. Don't call the number or tap anything in the pop-up. No genuine Microsoft warning tells you to call.
  2. Close the browser. If the page won't let you, force-close it (on Windows press Ctrl+Shift+Esc, pick the browser, and End task), then reopen without restoring the session.
  3. If you already called or gave remote access: disconnect from the internet, uninstall any app they installed, run a scan with the built-in Windows Security, and change your passwords from another device. Call your bank if you paid or shared card details.
  4. Report it. File at reportfraud.ftc.gov, and read Microsoft's own guide to tech-support scams.

Reduce the risk of another scam

A browser warning is not a reliable diagnosis of your device. Close the suspicious page and do not call its number or install its software. Keep the operating system and browser updated. If you downloaded something, granted remote access, or entered credentials, secure the device and accounts using official support; closing the page alone is not a guarantee that everything is clean.

● Public service · free steps first

Take the free protection steps first

A suspicious message does not tell us how someone found your details. If you shared personal information, start with the official recovery guidance. You can also freeze your credit for free.

Decide what protection you need

Start with the free controls above. Compare what a paid service would add only after deciding which problem remains.

Compare free and paid protection →

No purchase needed. How we use evidence.

Frequently asked

Is the Microsoft security warning pop-up real?
Microsoft says its error and warning messages do not include support phone numbers. Do not call a number displayed in a suspicious browser warning. Close the page or browser and use Windows Security or official Microsoft support to check the device; the fake alert does not prove it is otherwise clean.
The pop-up locked my whole screen — how do I close it?
It's controlling the browser, not Windows. Press Ctrl+Shift+Esc to open Task Manager, select your browser, and click End task. Reopen the browser and choose not to restore the previous session. If it keeps coming back, clear your browsing data and run a scan with Windows Security.
I called the number and let them connect to my computer — what now?
Disconnect from the internet, uninstall any program they had you install (often remote-access tools like AnyDesk or TeamViewer), and run a full scan with Windows Security. Change your important passwords from a different device, and if you paid or shared card details, call your bank to reverse it. Then report it at reportfraud.ftc.gov.
Will Microsoft ever call me about a virus?
Microsoft says it does not make unsolicited support calls to fix your computer. Hang up on a suspicious caller and reach Microsoft independently. Do not generalize that rule into a claim that every genuine subscription email, support response, or account notice is fake.

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Sources

  1. 01How To Spot, Avoid, and Report Tech Support Scams— Federal Trade Commission
  2. 02Protect yourself from tech support scams— Microsoft
  3. 03Report fraud to the FTC— Federal Trade Commission
  4. 04Internet Crime Complaint Center (IC3)— FBI
  5. 05How To Recognize and Avoid Phishing Scams— consumer.ftc.gov
  6. 06What To Do if You Were Scammed— consumer.ftc.gov

Pass it on

Help protect someone else

If this could have fooled you, it can fool someone you know — a parent, a friend, the family group chat. It's safe to forward, and stands on its own as a record for a bank or the police.