Software engineers often prioritize functionality over resilience, but application security demands a different mindset. The core goal is ensuring features cannot be subverted. This guide outlines essential pillars for building secure systems, focusing on the CIA triad, risk management, and the critical distinction between authentication and authorization. It aims to shift developers from building features to becoming the first line of defense.

Security starts with the CIA triad: Confidentiality keeping secrets safe, Integrity preventing data manipulation, and Availability ensuring access when needed. Since you cannot fix every flaw, Risk Management is vital. Using the formula Risk = Probability × Impact, developers must triage threats. This approach prioritizes critical vulnerabilities like SQL injection over minor issues, ensuring resources address the most dangerous weaknesses first.

Confusing Authentication (who you are) with Authorization (what you can do) creates major vulnerabilities. A driver’s license proves identity, while your age authorizes specific actions. Failures here, like IDOR attacks, are common. Developers must adopt Defense in Depth with multiple security layers, enforce the Principle of Least Privilege, manage secrets properly outside code, and validate all inputs to prevent injection attacks.