I'm from europe (the Netherlands). Everytime I see these american robocall threads it blows my mind. What about your system is so bad that allows this to go on? It's not a problem here at all.
They seem spoofed because you can see them increment the numbers and try again. Also they come from various countries both in and out of europe.
They always ring 2-3 times then hang up.
I've blocked dozens of them by now, they just come up with new numbers.
I don't understand what the point is because nothing happens if you call back so there's nothing to keep you on the line.
Also nothing happens if you respond.
I understand that these are all things I shouldn't do but a) at one point the numbers resembled those of RedHat in the UK and b) I was curious.