The issue, as I understand it, is that the SS7 telephone network is completely insecure assuming that you have the ability to connect to it. Shady gateway providers will allow you the privilege, and once you're in, you can do just about anything.
There is precious little within SS7 to prevent or respond to spoofing. It's a major nightmare for telephone companies.
There is precious little within SS7 to prevent or respond to spoofing. It's a major nightmare for telephone companies.