CGNAT: A Necessary Evil? The Security Implications of Carrier-Grade NAT

Facing an IPv4 address shortage, internet providers widely adopted Carrier-Grade NAT (CGNAT), mapping multiple users to a single public IPv4 address. While solving the address depletion problem, CGNAT presents significant challenges for law enforcement and security tools. A single IP address can represent thousands of users, rendering traditional IP-based identification, filtering, and configuration ineffective. This leads to difficulties in investigations, false positives in security systems, and interference with services like OpenDNS. The EU and other bodies are pushing for IPv6 adoption to mitigate the security risks associated with CGNAT.