I have a 15" 2017 MacBook Pro running OS 10.13.4: On a couple of occasions while using Safari, I have had a pop-up box appear that says my computer is blocked and that I need to call a certain telephone number to unblock it. I realize that this is some kind of scam, so I simply continue with what I am doing. However, whatever this program is, it dumps dozens, perhaps 100-200, files into my Downloads folder. These files bear the Safari logo and are labeled "unknown file." Has anyone else encountered this problem? Is there any way to prevent it from happening? Also, is there a way of emptying the Downloads folder of more than one file at a time? Apparently no malware is involved. At least nothing is detected in a Malwarebytes scan.