Defence in Depth

Defence in depth is the foundational strategy of network security architecture. It requires deploying multiple, overlapping layers of security controls so that if one layer fails, others continue to protect the network. No single control is expected to be perfect — the strength lies in the combination.

---

The Concept of Layered Security

Defence in depth is borrowed from military strategy where multiple defensive lines slow and attrit an advancing enemy. In network security, each layer adds friction for the attacker: