A pop-up says my computer has a virus. What do I do?
Answer first
Close the tab and do not call the number in the notice. A web page's own warning is not a trustworthy virus scan.
An ordinary web page does not run the operating system’s virus scan. An alert and phone number on the page therefore do not prove that the computer has malware.
The notice tries to make you call. The caller may then ask you to install remote-access software and pay for a repair.
Close the page and use the operating system’s own virus scan if needed. If you downloaded or installed anything, include that information when getting help.
If you have already rung and given somebody access to your computer, disconnect it from the network and change your passwords from another device.