The Microsoft support call

Someone calls, or a full-screen warning appears with an alarm sound and a number to ring. Your computer is infected. Your bank details are at risk. Fortunately they can fix it.

Microsoft does not know your computer has a problem. Neither does Apple, or BT, or your bank. They have no mechanism for knowing. That single fact ends every version of this.

How it plays out

The cold call. "We have detected a virus on your Windows machine." Often to landlines, often to older people, often with a convincing accent on the technical detail.

The full-screen warning. A web page that fills the screen, plays a siren, disables your back button and shows a support number. It is a web page. It has done nothing to your computer.

The fake purchase receipt. An email confirming a renewal you did not order, for £399, with a number to call and cancel. You ring them, which is the point — now it is your call, so you are not suspicious.

The dangerous moment

When they ask you to install remote access software. AnyDesk, TeamViewer, UltraViewer. From then on they are operating your computer.

What they then do:

• Open Event Viewer and point at the ordinary warnings every Windows machine has, as proof.
• Run a command that prints harmless output and describe it as a security scan.
• Open your online banking while you watch, and "refund" you too much by editing what the page

displays, then ask you to send the difference back.

• Install something that lets them return later.

The refund trick is worth knowing in detail, because it turns you into the person who transfers the money, which is much harder to reverse.

If it is happening right now

Hang up. Not "politely end the call" — hang up. You owe them nothing.

If a warning page has taken over the screen: press Escape to leave full screen, then close the tab, or force-quit the browser. Ctrl+Shift+Esc on Windows, Cmd+Option+Esc on a Mac.

If you already let them in

Work through this, in order:

1. Disconnect from the internet. Wi-Fi off, or unplug the cable. 2. Uninstall the remote access software. 3. Run a full scan with whatever anti-malware you have. Windows Defender is fine. 4. Change your passwords from a different device — your phone, not the machine they touched. Email first. 5. Ring your bank if you opened banking at any point, or if any payment was discussed. 6. Consider a full reset of the machine if they had it for a while. Tedious, and certain.

For an older relative

The useful sentence, said once, without drama: nobody legitimate will ever ring you about your computer. Not their internet provider, not Microsoft, not anyone. Any call about a computer problem is a scam, and hanging up is always the right answer.

Give them permission to be rude to strangers on the phone. That is the whole defence.