Be wary! These messages could be “scareware” designed to deceive you into downloading -- and paying for -- software that might turn out to harm your computer. Some scareware will even pretend to scan your computer and “find” viruses. So, don’t be fooled.

Whatever you do, don’t click on them -- even to get rid of them. Some of these ads have fake “x” buttons that would seem to close the window, but clicking on it actually takes you to a website, or even starts a download.

If you have a PC, use the Control + Alt + Delete combination to open the Windows task manager. Chances are, the pop-up is listed as a browser window, and you can close it by clicking “End Task.” You can do something similar on a Mac by using the “Quit” or “Force Quit” option and quit the browser application. If that doesn’t work, you may have to reboot to make the pop-up go away.