A common and persistent scam works by manufacturing a technical emergency and then offering to solve it. It takes two main forms. In one, a sudden pop-up appears while browsing - often full-screen, alarming, sometimes with a noise - warning that the computer is infected, compromised or about to lose data, and urging the user to call a phone number immediately or click to fix it. In the other, the phone rings and a caller claims to be from technical support, a software company or an internet provider, saying they have detected a problem with the computer and need to help sort it out. Both are built to create fear and urgency, because a frightened person in a hurry is less likely to stop and think.
The tell that unifies them is simple and worth holding onto: the contact came to you, unrequested, about a problem you did not report. Legitimate technology companies do not monitor a stranger's home computer and phone them when something is wrong, and a genuine security warning from your own device does not come with a phone number to call a stranger. A pop-up that appears out of nowhere and demands you call a number is not a real system alert; it is a web page designed to look like one. A cold call announcing that your computer has a problem is not support; it is the opening line of the script. The unrequested contact is not the prelude to the scam - it is the scam.
The goal in every case is one of two things: to get remote access to the computer, or to extract a payment. If the victim calls the number or lets the caller proceed, they are typically talked into installing software that hands the scammer control of the machine, at which point the scammer can rifle through files, install harmful programs, or fake a problem to justify a fee. Or they are simply pressured into paying for unnecessary "repairs", "protection" or "refunds", often by a method that is hard to reverse. The access is the dangerous part: a person who has been given remote control of a computer can do a great deal of damage and see a great deal of private information.
The defence needs no technical skill. For an alarming pop-up, do not call the number and do not click its buttons; close the browser - and if it will not close, shut the device down and reopen it - and the fake warning is gone, because it was only a web page. For an unsolicited call about a computer problem, hang up; no genuine support works this way, and there is no rudeness in ending a call you did not ask for. Never grant remote access to someone who contacted you unprompted, and never pay for a problem a stranger told you about out of the blue. If there is any worry about the device, contact a technician you have chosen and trust, through a number you looked up yourself - not one that appeared on a screen or was given by a caller.