Without going into too much detail there's a master carrier caller ID database maintained by neustar, formerly Lockheed Martin information systems, but that reg

Without going into too much detail there's a master carrier caller ID database maintained by neustar, formerly Lockheed Martin information systems, but that registry is hilariously bad and expensive, so people cache caller ID in secondary databases and perform "dips" against these janky databases for cash. This doesn't even take into account the problem that sending an arbitrary caller ID is trivial and verifying ownership of a given caller ID is impossible (this is a design choice inherent to SS7 having caller ID bolted on after the fact). In short, no, not an easy problem.