That isn't an easy problem to solve.
What do you do when a company has a large set of numbers on a single trunk? Do you maintain a list of authorized CID source numbers? How do you enable 3rd parties to make calls on your behalf?
What do you do when a company has a large set of numbers on a single trunk? Do you maintain a list of authorized CID source numbers? How do you enable 3rd parties to make calls on your behalf?
Why should that be possible? If anything the disadvantages of nuisance or even scamming obviously far outweigh the benefits.
We once had a customer that set their callerID name to "DEAD" to signal that the phone number was no longer in use. People thought they were issuing threads on their outbound calls.
I see how it's a hard problem to solve in 100% of cases, but I don't see why it's not solved for most of them. Carriers have their own interconnects, pricing, and contracts. I believe 99.99% of call spam can be solved in a few months by major telcos coming up with a definition of spam callers and updating contracts to say: if you route more than N such calls within M days, and don't report who you disconnected because of it, we're disconnecting you instead. Real small telcos would have to drop misbehaving lines immediately. Fake telcos selling services only to spammers could not continue to do business.