Re: "ransomware...as a Windows screensaver"
I've got news for you. They still fall for "U can haz codec, yes?" and "FREE!!1! Antivirus scanner." too.
All now older than the hills and giving the mountains a run for their money.
Unfortunately nobody has yet built an OS that's proof against "Yes of course I want that installed and I'm happy to grant you the privilege to do it!".