Grey Routing

Grey routing is the unauthorised termination of voice or SMS traffic via routes that bypass official interconnect agreements, often abusing roaming or wholesale arrangements to deliver traffic at lower cost. It deprives the destination operator of expected termination fees and degrades CLI integrity. Detection relies on test-call generators and traffic-pattern analytics on the SMSC and gateway MSC.

Categories: Radio Access NetworkCore NetworkRoaming and Interconnect

Grey Routing 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 Grey Routing in the wider telecom-security picture, review GTP Firewall, GTP-U Smuggling, AUSF, IBCF, Red Team and Threat Intelligence.

Related terms

Related topic hubs

  • SMS Firewall SMS spam, phishing, A2P bypass and MAP-layer SMS filtering.
  • Roaming Security IPX/GRX interconnect risk, home-routed vs local-breakout, SEPP.
  • Signaling Firewall Unified SS7/Diameter/GTP/SMS signaling firewall framework.
  • Telecom Fraud IRSF, Wangiri, SIM box, PBX hacking and CLI spoofing.

More from the TelcoSec Glossary

Browse the full TelcoSec Glossary, the Ultimate Guide to Mobile Network Security, or the P1 Arsenal of telecom-security tools.