Indeed, SS7 is based on a whole host of assumptions that just can't be relied upon. Since SS7 doesn't even bother to try to verify who anyone is (you'd only pee

Indeed, SS7 is based on a whole host of assumptions that just can't be relied upon. Since SS7 doesn't even bother to try to verify who anyone is (you'd only peer with trustworthy people, right?!), it's also very hard to hold anyone accountable too. And since the idea of SS7 signalling is that it can be forwarded and passed around, it simply needs to be replaced by authenticated, access-control validated signalling. Then you can at least have some confidence you're actually hearing from a network that has a reason to be communicating. Too much of SS7 comes from a world where anyone can do anything - there's no legitimate reason in 2021 for an arbitrary network to be able to request a user's network location and cell ID, but the protocols support it. SS7 firewalls try to plug the gaps, but ultimately you just innovate in how you try to get the network to hand over what you want, and eventually you'll find a way the firewall doesn't spot. Cat and mouse continues. Telco networks are "zero trust", just not in the right way(!)