Defense in Depth

Defense in depth is the strategy of layering multiple security controls so that if one fails, others continue to protect your systems and data. Rather than relying on a single defensive measure (like just a firewall), you implement multiple overlapping protections — firewalls, endpoint protection, access controls, encryption, monitoring, training, and physical security.

The idea comes from military strategy: multiple defensive lines are harder to breach than a single wall. In cybersecurity, this means an attacker who gets past your firewall still faces endpoint protection, who then faces access controls, who then faces encryption, and so on. No single control is perfect, but together they create a formidable defense.