Defense in Depth is a cybersecurity strategy that employs multiple layers of security controls throughout an IT system. The principle is that if one defense mechanism fails, another will be in place to thwart an attack. This approach recognizes that no single security measure is infallible. Key components include: 1. Physical controls: Barriers, guards, locks, and surveillance systems 2. Technical controls: Firewalls, IDS/IPS, antivirus, encryption 3. Administrative controls: Policies, procedures, awareness training Implement this principle by mapping your security architecture and identifying where single points of failure might exist. Then add complementary controls that provide overlapping protection.