The A in SS7 stands for authentication. It's old enough that it predates any kind of meaningful network security practices. You can amend the standard to add au

The A in SS7 stands for authentication. It's old enough that it predates any kind of meaningful network security practices. You can amend the standard to add auth (that's what SHAKEN does), but the issue has been that much of the equipment carrying these calls was built back when C was a hot new language and people rode dinosaurs to work. Some telcos based their entire business model on putting off the upgrades and none of the legitimate telcos would cut them from the network, so the FCC (eventually) stepped in.