What are the 5 basic principles of security?

What are the 5 basic principles of security are core concepts that guide protection efforts across physical and cyber domains. While models vary, a common set includes Confidentiality ensuring information is only accessible to authorized users, Integrity ensuring data is accurate and not tampered, Availability ensuring systems and data are accessible when needed, these three form CIA triad. The fourth is Authentication verifying identity of user or device, and fifth is Non repudiation ensuring actions cannot be denied. Another widely taught 5 principles are Least Privilege giving users only minimum access needed, Defense in Depth layering multiple defenses so if one fails another protects, Separation of Duties dividing critical tasks between multiple people to prevent fraud, Security by Design building security in from start not as afterthought, and Fail Secure ensuring system fails to secure state rather than insecure. For physical security, principles are Deter, Detect, Delay, Deny, Defend. All principles aim to reduce risk by limiting access, verifying trust, maintaining accuracy, ensuring resilience, and planning for failure. Applying these consistently creates robust security posture that protects against both opportunistic and determined threats.