Scam calls and pop-ups saying your computer is infected: what to do

24 July 20267 min read

A phone call from someone saying they are from a technology company and your computer has a virus. A message that fills the screen, makes an alarm noise, and gives a number to ring. Both are designed to frighten you into acting before you think, and both are scams. If one has happened to you, you have done nothing wrong. Here is how to recognise them and what to do.

Nobody legitimate rings you about your computer

This is the one rule to remember, and it covers almost every version of the scam. No technology company monitors your home computer, knows your phone number, and rings you about a problem. Not the company that made the computer, not your broadband provider, not your bank's technical department. If a call about your computer arrives and you did not ask for it, it is a scam, however polite or convincing the person sounds.

They are good at this. They use real-sounding job titles, read out numbers from your own computer that mean nothing, and stay friendly right up to the moment you say no. Some claim you are owed a refund, some say your broadband is being used by criminals. It does not matter which story it is. Put the phone down. You do not owe a cold caller an explanation, and hanging up mid-sentence is not rude.

A full-screen pop-up with a phone number is always fake

The other version appears while you are browsing. The screen fills with a warning, often with a logo you recognise, telling you that your computer is infected or locked and that you must ring the number shown. One detail gives it away every time: real security software never asks you to ring a phone number. Never. If there is a number on the warning, it is a scam, and it belongs to the people running it.

These pages are just a website designed to look alarming. In most cases your computer is not infected at all. You have landed on a bad page, often through a mistyped address or an advert.

How to close one safely

The important part is what you do not do. Do not click anything inside the message, including the cross in the corner or anything saying cancel or scan now. Those are part of the page, not part of your computer. Close it from the outside.

On a Windows computer, hold Ctrl and Alt and press Delete, choose Task Manager, select the web browser in the list and choose End task.
On a Mac, hold Command and Option and press Escape, select the browser and choose Force Quit.
If neither of those works, you can hold the power button in for several seconds to switch the computer off, then switch it back on. Do this last, because anything you had open and not saved will be lost.
When you reopen the browser, if it offers to restore the previous pages, say no: that brings the same page straight back.

Once it is closed, run a scan with the security software already on the computer; on Windows the built-in protection is fine.

Never let a cold caller onto your computer

A scam succeeds the moment you install something that lets them control your screen. They will call it a diagnostic tool or a security check. What it does is hand the keyboard and mouse to a stranger, who can then open your email, your files and your banking. Everything they show you afterwards is theatre to justify a payment.

Remote access itself is not a bad thing. It is how a great deal of honest support is delivered, including ours. The difference is who started the conversation. If you rang a company you chose, using a number you looked up yourself, that is normal. If someone rang you, it is not.

If you have already let someone in

Act, but do not panic. Take these steps in order.

Disconnect the computer from the internet: unplug the network cable, or switch off the wifi or the router.
Ring your bank straight away if you paid, if you gave any card or bank details, or if online banking was open or saved on that computer. Use the number on your card or statement, or dial 159, and never a number the caller gave you.
Change the passwords for your email and your banking from a different device, such as a phone or tablet, not the affected computer. Start with email, because it is the master key that resets everything else.
Switch on two-step sign-in for your email and your bank if it is not on already.
Get the computer checked, so anything they installed is removed rather than assumed gone.
Report it to Action Fraud.

Telling a real warning from a fake one

Genuine warnings from your computer are calm and boring. They appear in a small window in the corner or in the taskbar, and they never give you a phone number to ring. That is the reliable test. A fake also tends to fill the whole screen, count down, and press you to act immediately, but the phone number is the tell that holds every time.

If you are not sure, ask someone. Ring a family member, a neighbour, or us. Nothing bad happens while you take five minutes to check with another person, and that pause is exactly what a scam is designed to stop. We can help people across Sutton Coldfield and the surrounding West Midlands with this, and we are happy to tell you a message is nothing to worry about.