Defense in Depth and Layered Security

Defense in depth is the practice of layering multiple, independent security controls so that if one fails, others still protect the system. No single defense is perfect, so you never rely on just one.

Think of a castle: a moat, walls, guards, and a locked keep. An attacker who passes one barrier still faces several more before reaching anything valuable.

A layered network might combine a perimeter firewall, network segmentation, intrusion detection, endpoint antivirus, strong authentication, encryption, and user training. Each layer covers a different angle of attack.

The goal is that no single weakness, like one stolen password or one unpatched server, hands an attacker the whole network. Each control buys time and chances to detect the intruder.