While surfing the web on your computer or mobile device, if you've ever seen one of these pop-ups, you've navigated to an unsafe web page and need to shut down your browser and, preferably, run an antivirus scan on your device.
If you actually call the toll-free number, you're well on your way to becoming a victim of credit card fraud and worse, especially if you let the "Tech Support" person on the other end of the phone remotely control your device.
Would you let a complete stranger into your house, in the dark of night where you can't even see his face, just because he knocks on your door and says, "your burglar alarm has been hacked?" I didn't think so.
Even Apple devices can display these fake warnings.
This type of ruse is called scareware. (You should google that.) I've known a number of people fall victim to the "tech support scam," and it never ends well, requiring some level of security clean-up afterward.
When you receive an unexpected email or a pop-up carrying a threatening message like this, please stop what you are doing and remember that things are not always what they seem. Don't pick up the phone and don't click links. Shut down the app (ALT+F4 in Windows, Command+Q on Mac).
Security experts at Sophos recently posted an informative article about how to spot fake web pop-ups. Take a look at one the recent examples Sophos provides, like this one:
For more information, read the full article at https://nakedsecurity.sophos.com/2020/09/09/fake-web-alerts-how-to-spot-and-stop-them/. Stay on your guard.