possible security breach

The phone number shown in that pop‑up should be treated as part of a tech support scam, not as a legitimate Microsoft number.

Microsoft guidance states that:

• Microsoft does not send unsolicited messages or make unsolicited phone calls to provide technical support or request personal/financial information.
• Error and warning messages from Microsoft never include a phone number to call.

The behavior described—sudden pop‑ups, warnings that the computer is breached, instructions not to close the browser, and a number to call—matches known tech support scam tactics.

What to do now:

1. Do not call that number and do not provide any personal, financial, or password information.
2. Close the browser:
   • Try Alt+F4 to close the window, or
   • Press Ctrl+Alt+Del, open Task Manager, and end the browser process.
3. If the browser won’t close, restart the computer.
4. After restart, reopen the browser and decline any prompt to “restore previous pages.”
5. Optionally, clear the browser cache and run a scan with Microsoft Defender.
6. Report the scam to Microsoft at https://www.microsoft.com/reportascam.

If remote access was not granted and no software was installed at the scammer’s request, the system is typically not compromised; the pop‑up itself is just a malicious web page.

References:

• Protect yourself from tech support scams
• Protect yourself from online scams and attacks
• Tech support scams
• Microsoft Defender Scam or Do I have a virus on my computer - Microsoft Q&A
• How do I report a possible scam from Microsoft? - Microsoft Q&A
• Who do I call for support? - Microsoft Q&A
• why can't you block AnyTech365.com....they are a scam company posing as Microsoft supported, stealing information? - Microsoft Q&A