If the alert included a phone number, told you to call support, or appeared as a pop-up that blocked the screen, treat it as a scam. Genuine Microsoft error messages do not include a phone number to call.
What to do:
- Do not call any number and do not click links in the alert.
- Close the browser or app showing it. If it will not close, open Task Manager with Ctrl + Shift + Esc, find the browser, and select End task.
- When reopening the browser, do not restore the previous tab or session, or the scam page may reopen.
- If the pop-up keeps returning, clear the browser cache/cookies or reset the browser settings. One documented path is Settings > Apps > Installed apps > select the browser > Advanced Settings > Reset.
- Run a Windows Security / Microsoft Defender scan for reassurance.
- If the alert was an email claiming to be a Microsoft account security alert, verify it carefully before acting. Hover over links and buttons to confirm they reference Microsoft, and review message headers or tracking details if available.
- If the alert was a real Windows Security notification, open Windows Security > Protection history and check the alert type:
- Threat blocked: the threat was blocked and removed; no action is necessary.
- Remediation incomplete: open the card and follow the additional steps shown.
- An important service is off: open the card and turn the feature back on under Actions.
If the alert was only a warning bar inside an Office app, it may be a security alert or policy tip that can be managed from Office Message Bar settings.
- Avoid and report Microsoft technical support scams
- Protection History in the Windows Security App
- You receive a Microsoft account security alert email message in Office 365 Dedicated/ITAR (vNext)
- .How can I remove scam Windows Defender security alert from screen? - Microsoft Q&A
- Turn on or off security alerts and Policy Tips in the Message Bar for Office