Security by Design means building security controls into systems from the beginning rather than adding them after development is complete. Security is far cheaper and more effective when it shapes design decisions from the start.
In practice, developers consider authentication, input validation, encryption, and error handling as core requirements alongside functionality. Threat modeling happens before coding begins. Security reviews occur at each development stage.
CISSP Relevance
Security by Design is foundational in Domain 8 (Software Development Security) and Domain 3 (Security Architecture and Engineering). CISSP candidates must understand secure development lifecycle practices and how to integrate security into engineering processes.
External reference: CISA Secure by Design Principles
Related terms: Threat Modeling, Security Baseline