SIGNALING SECURITY HUB

Securing the signaling plane requires a defense-in-depth approach that combines active monitoring, strict protocol filtering, and modern cryptographic protections. Historically, SS7 and Diameter network connections were trusted implicitly, allowing any connected carrier to request sensitive subscriber information. In modern deployments, operators must implement Signaling Firewalls (under GSMA FS.11 guidelines for SS7 and FS.19 for Diameter) to inspect, rate-limit, and validate the source of all incoming routing messages.

A critical control is Cross-Layer and Velocity Validation. This involves verifying whether the physical location of the subscriber matches the routing requests sent by the network. For example, if a Send Routing Info for SM (SRI-SM) message for a specific MSISDN originates from a foreign network, the firewall must verify if that subscriber has recently registered a location update in that geographic region. If the velocity required to travel between the last known location and the new request source exceeds physical limits, the request is flagged as an active tracking attempt and blocked.

With the transition to the 5G Service Based Architecture (SBA), legacy binary protocols are replaced by HTTP/2 RESTful APIs running over TLS. While this eliminates many of the structural vulnerabilities of SS7/Diameter, it introduces new web-centric threat vectors, such as API parameter tampering, token leakage, and unauthorized registration of rogue Network Functions (NFs) in the Network Repository Function (NRF). Enforcing mutual TLS (mTLS), implementing OAuth 2.0 authorization, and deploying Security Edge Protection Proxies (SEPP) at interconnect boundaries are essential steps in securing inter-operator 5G roaming interfaces.