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 instructions that set up calls, register subscribers, hand over sessions 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 FS.11 / FS.19 / FS.20 as a top-tier telecom risk.

Roaming and interconnect are where two operators, often with an IPX or GRX carrier in between, 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.

Related terms

Equipment

GRX/IPX edge, DNS and ENUM

Articles in the P1 mobile network security guide

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.

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.