ENUM (E.164 Number Mapping)

Also known as: E.164 Number Mapping, Carrier ENUM, Infrastructure ENUM

ENUM is the IETF mechanism (RFC 6116) that maps an E.164 telephone number into DNS to discover SIP URIs and other service URIs associated with it. Carrier ENUM (also called Infrastructure ENUM) is used for IP interconnect between operators to route calls directly over SIP rather than falling back to TDM. Compromise of ENUM data or the DNS resolvers behind it can enable large-scale call rerouting, interception and IRSF fraud.

Categories: SignalingRoaming and InterconnectProtocols and Standards

ENUM in context

Signaling protocols carry the control-plane messages that set up calls, register subscribers and route SMS. SS7, Diameter, GTP-C and SIP are the four dominant families, and interconnect exposure of any of them is treated by GSMA as top-tier telecom risk.

Roaming and interconnect are where two operators exchange signaling and user-plane traffic. Trust boundaries here are the primary attack surface for location tracking, SMS interception and fraud, which is why GSMA now mandates SEPP with PRINS on 5G interconnect.

To place ENUM in the wider telecom-security picture, review CAMEL, HLR, ISUP, Roaming, SS7 and N32-f: each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

Related topic hubs

  • Roaming Security IPX/GRX interconnect risk, home-routed vs local-breakout, SEPP.
  • Telecom Fraud IRSF, Wangiri, SIM box, PBX hacking and CLI spoofing.
  • SS7 Security SS7/MAP/CAP/SCCP attacks and defenses across 2G/3G interconnect.
  • SS7 Firewall GSMA FS.11 category 1/2/3 SS7 message screening at the STP edge.

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