CIA Triad — The three pillars of security:

Confidentiality: Only authorized access — encrypted with AES, protected by ACLs
Integrity: Data not altered — verified by hashing (SHA-256), digital signatures
Availability: Accessible when needed — ensured by RAID, failover, backups

Security Controls

By Type: Technical (firewalls, encryption) · Administrative (policies, training) · Physical (locks, guards)
By Function: Preventive · Detective · Corrective · Deterrent · Compensating

Risk Management

ISC2 Code of Ethics (4 Canons — in priority order)

Key Principles: Least privilege · Separation of duties · Defense in depth · Need-to-know · Due care vs Due diligence

Cryptography Basics: Symmetric (AES — same key) · Asymmetric (RSA — key pair) · Hashing (SHA-256 — integrity) · TLS (in-transit encryption)