A pop-up says your computer is infected. Should you call that number?

The problem

The screen fills with a warning, sometimes with a siren sound or a voice that will not stop repeating itself. It says the computer is infected, or locked, or that personal files are being stolen right now. Underneath is a phone number and a countdown clock, both urging the same thing: call before it is too late.

Calling connects to someone who sounds calm and technical. They ask for remote access to "run a scan," then narrate a list of frightening problems they claim to have found. What follows is either a bill for fake repairs, a request for payment in gift cards, or, if they get deep enough into the computer, access to online banking and saved passwords.

None of it started with a real problem. The pop-up itself is the scam.

How it can happen

These warnings do not come from an actual virus. They come from a bad ad on an ordinary website, a pop-up that a browser failed to block, or a link clicked by accident. The page is built to look like it came from Windows, Microsoft, or Apple, right down to the logo and the colour scheme, but it is just a web page like any other, dressed up to look like a system alert.

The FTC is direct about the tell: a real security pop-up never asks you to call a phone number. Genuine tech companies do not contact people by phone, email or text message to say there is a problem with their computer, and they never leave a support number inside a warning box on screen. The countdown timers and sirens exist for one reason, to create enough panic that nobody stops to check that basic fact.

How to avoid it

Do not call the number. Close the browser tab. If the browser has frozen and will not close normally, restart the computer rather than clicking anything inside the warning itself, since some fake pop-ups are built so that every button, including an "X" or "Cancel," triggers the same download.

If the computer is genuinely running slowly or behaving oddly afterwards, that is a separate question worth checking properly. Take it to a trusted local repair shop, or contact the manufacturer through the support number on their real website, typed in directly rather than searched for or copied from a pop-up. Never install software, and never grant remote access, to anyone who contacted you first.

A password manager and up to date antivirus software from a company you chose yourself, not one that popped up on screen, do more to protect a computer than any call placed in a panic.

Things to watch

• A phone number written inside a warning message on screen.
• A countdown timer or a siren sound meant to rush a decision.
• Any request for remote access to fix a problem nobody reported.
• A demand for payment in gift cards, wire transfer, or cryptocurrency.
• A pop-up that will not close normally, or reopens every time it is closed.

If you have already called a number like this and let someone access your computer, read our guide on what to do after you shared a code or gave someone access.