Your case sounds like run-of-the-mill malware that hasn’t really done anything to your computer at that stage. It just comes up as a pop-up and pretends to have found various scary-sounding viruses. They are hoping you will contact them, whereupon they will talk you into downloading and installing their “antivirus” software, which will then steal personal information, credit card numbers, passwords, etc. (if these are saved somewhere on your computer). They’ll also charge you for the “privilege” of being robbed while they’re at it.
Wouldn’t doubt it.
I didn’t think it was a legit threat. My thought is, if you get a ransom note, you’re goose is probably already cooked.
I’ve also gotten the pop up on the screen that states it’s from Microsoft, and urges you to clean your computer right away, (and here’s a link...).