ADC stands for Application Delivery Controller. It is a network appliance or software layer that sits between users and backend services to manage how application traffic is routed, balanced, protected, and optimized. Common ADC features include load balancing, TLS termination, SSL bridging, reverse proxying, health checks, and sometimes a Web Application Firewall.
ADC devices matter in cyber security because they sit on a high-trust path: they handle both application requests and administrative control. If an attacker exploits an ADC flaw, they may be able to intercept traffic, disrupt service, weaken security controls, or reach management functions. Defenders rely on ADCs to enforce access rules, filter malicious requests, and absorb traffic spikes, but those same capabilities make them high-value targets. Keeping ADCs patched, limiting admin exposure, and verifying the correct release branch are essential defensive practices.