Re: And the operators that allowed the spoofing?
Back when I still had a copper landline, I had a device which prior to letting the call ring through, sent whatever the tone was to indicate a disconnected number. It had no effect on humans dialing my number The robocallers would move on to the next number in their list. Over a period of time, the "disconnected" number was promulgated and dropped from the spamming database(s). I went from several spam calls a day to one or two in a month. I have no doubt the telcos could do something similar for the cellular network, but just like those days of yore, it would decimate their bottom lines whereas the few hundred (thousand?) of us doing it privately didn't register with the beancounters.