What is the CIA triad in security?

The CIA triad is the foundational model of information security, representing three core principles. Confidentiality: ensuring data is accessible only to authorized parties — achieved through encryption, access controls, and authentication. Integrity: ensuring data is accurate and has not been tampered with — achieved through hashing, checksums, digital signatures, and access controls. Availability: ensuring systems and data are accessible to authorized users when needed — achieved through redundancy, failover, backups, and DDoS protection. Every security control, policy, and technology maps back to one or more of these three principles. Some models extend this to AAA (Authentication, Authorization, Accounting) or add Non-repudiation as a fourth pillar.