TCAP (Transaction Capabilities Application Part)

Transaction Capabilities Application Part is the SS7 layer that supports remote operations and dialogues between network elements, sitting on top of SCCP and underneath application protocols such as MAP and CAP. TCAP carries the begin, continue, end, and abort messages that frame each transaction. Because it has no authentication of its own, attackers with SCCP-level reachability can use TCAP as a vehicle for unauthorised MAP queries, location tracking, and fraud, making TCAP-aware filtering a core function of any SS7 firewall.

Categories: Radio Access NetworkCore NetworkSignaling

TCAP in context

The radio access network is the layer where mobile devices attach to the operator's infrastructure. Attacks in this layer include IMSI catching, rogue base stations, downgrade attacks and jamming, and defenses hinge on mutual authentication, integrity-protected signaling and Open RAN supply-chain hygiene.

The mobile core is where subscriber sessions, mobility and policy live. In 4G it is the EPC (MME, HSS, S/PGW); in 5G it is the Service-Based Architecture with AMF, SMF, UPF, AUSF, UDM and the NRF. Core exposure is the difference between a single-subscriber leak and a fleet-wide breach.

To place TCAP in the wider telecom-security picture, review AMF, NRF, SC, CSCF, Service-Based Architecture (SBA) Security and TLS.

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