Where do they come from? Not even a dodgy site... They hold your browser to ransom till you pay them money. Obviously a 'force close', does the trick, but you do get a spinning wheel for a few more minutes on other sites, so wonder if it does anything to Macs? Presume it doesn't leave anything on the computer after unless its a Windows computer?
If anyone not aware
https://www.youtube.com/watch?v=uK5iP-CmtTM
Also an 'FBI' version for our friends across the pond
If anyone not aware
https://www.youtube.com/watch?v=uK5iP-CmtTM
Also an 'FBI' version for our friends across the pond