Having written several of these systems, there is nothing special about this software (NP databases). They maintain records of where a phone number is homed, no

Having written several of these systems, there is nothing special about this software (NP databases). They maintain records of where a phone number is homed, nothing else. There is more information in the white pages. In fact, NP databases typically won't have access to all phone numbers anyways, only those for customers who have changed providers. Everything else would be covered by the default routing rules. In the US, the central database is not involved in call control (I've never seen a design that was). Since phone companies are very risk averse, they don't generally allow software they don't control into the middle of their interactions with the customer. Phone companies will have their own mirrors of the database and purchase (typically bespoke, typically outsourced) systems to perform the in-call lookups. Reading up how the US works, it's an exception based system, with records only for ported numbers [1]. A typical record will look like: (408) 555 1212 -> (715) 555 1212 The destination number is not a phone number, and has the granularity of a single switch. No names, or anything else. I'm guessing this isn't about information leakage, because there's no information to leak. This isn't about DOS because the national database isn't involved in call control. This isn't about serving warrants either, it's operated locally. I can only imagine that this is a trade barrier masquerading as security, since switch software is produced offshore, and that's riskier. [1]https://www.npac.com/number-portability/how-lnp-works https://www.npac.com/number-portability/how-lnp-works