On Tuesday I had switched off AVAST protection on my Win7 laptop just to check if Microsoft Security was worth a trial - it was not! I went back to AVAST free, and I'm still happy with it!
When I googled for some guidance to set up Mac OS on VMware I suddenly got a pop-up that was even talking to me: Your PC got attacked by "Wanna cry ramsomware", don't use your mouse or keyboard, don't shut down or restart, just call this number (local Swiss phone number).
Just for the fun of it I called them, an Indian guy (acc to dialect) picks up and states being a Microsoft support agen - and how ultra-critical my situation was.
He asks me to open my browser on "fastsupport.com" on which a should install a remote control SW and pass control to him, which I did - eager to see what he would do.
He opened up a notepad sheet to list a number of expensive subscription models for multi-years MS AV support and asked for my credit card. I asked him to show me evidence that he was actually an official MS agent but he failed - as expected. All web forms and docs he showed me had whatever URLs but not from MS.
At this point I cut off the internet connection, uninstalled the 2 SW packaged received and hung up the phone.
Bottomline: they do have talking models that might convince some people, just to steal their money without even having viruses or ransomware at hand!
Best regards
5crambler