This post may actually be of some use (to those of you using Safari on a Mac anyway). Yesterday, I had the awful experience of a pop-up that I couldn’t get rid of. It said that I had to call a number right away to protect my identity etc. etc. I’d heard about malware that got on your computer encrypting everything so you couldn’t use it, except to pay them a ransom.
So I tried quitting Safari and restarting. No luck. There it was along with sites I always go to on Safari (PNAS, Nature, Science, Cell and Neuron).
So I tried to shut down (which wasn’t possible because I got a note that Safari was busy).
Then I used Force Quit to shut down Safari and was then able to shut down.
Rebooting was of no help whatsoever, as the pop-up appeared along with all 5 sites I usually have open whenever I opened Safari. This happened several times, yours truly being bull headed enough to try it again and again against all hope.
Time to call Applecare — they fixed it immediately. Apparently Safari has a some sore of cache which reopens everything you’ve opened on your last visit. This is what brought up my favored sites and the annoying popup.
The trick is to Open Safari from the Dock (and you must do it this way, not from recently used items) with the shift key held down — this flushed the cache (and the pop-up along with it).
Applecare said this pop-up wasn’t malware, just a scam which charged money to get rid of it (which you can now do free of charge).