CGNAT (Carrier Grade Network Address Translation)

Carrier Grade NAT lets a single public IPv4 address be shared by many subscribers, mitigating IPv4 exhaustion. While necessary in IPv4-only deployments, CGNAT complicates abuse attribution (multiple subscribers behind one public IP), undermines lawful-interception logging precision, and causes problems for inbound services. IPv6 deployment is the long-term answer.

Categories: Identity and SubscriberThreats and AttacksInternet and Routing

CGNAT in context

Subscriber identifiers (IMSI, SUPI, MSISDN, IMEI) are the anchor for authentication, charging, lawful interception and fraud analytics. Any protocol or interface that leaks a permanent identifier is treated as a serious privacy defect, which is why 5G introduced SUCI concealment on the air interface.

Telecom threats range from opportunistic SMS phishing and SIM swap to nation-state grade location tracking and lawful-interception abuse. The common thread is that most attacks exploit the inherited trust model of legacy signaling. SS7 and Diameter were designed for a closed operator community that no longer exists.

To place CGNAT in the wider telecom-security picture, review Sinkhole, Cybersecurity, Event Logging, IP Address, MNP and NAT.

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