A mediation tool is a component that sits between two parties and shapes how they communicate. In cyber security, that may be a proxy, gateway, broker, relay, or filter that forwards, transforms, or blocks data instead of letting endpoints talk directly. The tool can enforce authentication, log activity, translate protocols, scrub unsafe content, or apply policy before a message reaches its destination.
It matters because mediation changes the trust boundary. Defenders use it to reduce exposure and to inspect traffic in email security, web filtering, API gateways, and secure remote access. Attackers also value it: a compromised or fake mediator can intercept credentials, alter requests, downgrade protection, or exfiltrate data while appearing legitimate. Because it controls the path between systems, a mediation tool is often a high-value target and must be tightly secured and monitored.