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Defense in Depth
Definition
Defense in depth is a security strategy applying multiple layers of security controls. If one layer fails, the other layers still protect the system.
Defense in depth is a security strategy applying multiple independent layers of security controls so that failure of any single layer does not result in compromise. The concept derives from military strategy: if the enemy breaches the first line, they are stopped by the next.
How does defense in depth work?
Defense in depth stacks security measures at multiple levels: physical security, network security (firewalls, IDS/IPS, segmentation), endpoint security (EDR, antivirus), application security (secure coding, WAF), data security (encryption, DLP), identity security (MFA, IAM, PAM) and awareness (security training). Each layer provides protection when the previous one fails.
Impact on organisations
Organisations relying on a single security layer are vulnerable to attacks that bypass it. A firewall alone does not stop phishing. Antivirus alone does not stop zero-days. Defense in depth forces attackers to breach multiple barriers, increasing detection chances and attack costs. NIS2, ISO 27001 and NIST CSF are all based on layered security principles.
Protection
Regularly evaluate each layer through pentests and assessments. Ensure layers operate independently. Integrate layers via SIEM and XDR for correlated detection.
How DEFION helps
DEFION evaluates layered security through Security Assessments and pentests. Red Teaming tests the entire defense-in-depth from an advanced attacker's perspective.