Neither a SIP trunk nor a cellular modem confer access to SS7, which is used internally between telcos and is limited to access only by those telcos. The majori

Neither a SIP trunk nor a cellular modem confer access to SS7, which is used internally between telcos and is limited to access only by those telcos. The majority of VoIP providers, SMS aggregators, and other telephone-adjacent companies do not have SS7 access either as it is traditionally limited to wireline telcos, so they must contract a telco to perform those services for them. SS7 routing is strictly static and addresses are statically assigned, meaning that gaining unauthorized access to the network with a new device is usually not feasible (there would be no routes for traffic to reach it). Instead, SS7 access is usually gained by either locating a crooked telco, or compromising a device within a telco. While SS7 has essentially no security features, the primary security measure is the difficulty of accessing the SS7 network since it is entirely based on address management and routing by central authorities. This has been sufficient to slow the pace of SS7 vulnerabilities but not at all to stop them, as both crooked telcos and telcos with poor security practices can be found throughout the world.