A relay network is an intermediary communications path that forwards data between two endpoints instead of connecting them directly. In cyber security, relays are common wherever traffic must cross trust boundaries, reduce exposure, or hide the real source and destination of a connection. Examples include proxies, mail relays, VPN hops, and anonymizing overlays.
Relay networks matter because they can improve availability and segmentation, but they also create opportunities for abuse. Attackers use relays to mask infrastructure, bounce command-and-control traffic, and chain compromised systems so defenders see only the last hop. Defenders use relays to enforce policy, inspect traffic, and protect internal systems from direct contact. Security teams therefore watch relay paths for authentication misuse, unexpected routing, weak encryption, and single points of failure.