Peering is a direct arrangement between two networks to exchange traffic without sending it through a third-party transit provider. It is a core part of internet interconnection and is often set up at a Point of Presence, internet exchange, or private cross-connect. Peering can be settlement-free or paid, but in both cases it defines who can hand traffic to whom and under what routing rules.
In cyber security, peering matters because it shapes trust, reachability, and control. A weak peering setup can expose routes, leak traffic, or create an unexpected path into services that were assumed to be isolated. Defenders use strict prefix filtering, route validation, segmentation, and monitoring to prevent hijacks or misconfigurations from affecting traffic. Attackers may try to abuse routing mistakes, impersonate a peer, or exploit overly broad interconnection to reach internal systems. Good peering governance keeps expansion useful without turning connectivity into a security gap.