A Secure Software Development Lifecycle (SDLC) is a development process that embeds security activities into every phase of building software, from requirements and design through coding, testing, deployment, and maintenance, rather than testing for flaws only at the end.
In each phase a specific practice applies: security requirements and abuse cases up front, threat modeling during design, secure coding standards and static analysis while developers write code, dynamic testing and penetration tests before release, and patch management once the product is live. The payoff mirrors security by design, since defects found early cost a fraction of those found after deployment. A recurring mistake is treating a single security scan as if it satisfies the whole lifecycle. One tool at one gate cannot make up for insecure requirements or an architecture that was never threat modeled. Frameworks like Microsoft SDL, OWASP SAMM, and NIST guidance give teams a structured way to make these activities repeatable.
Why does the secure SDLC matter for the CISSP exam?
It is the backbone of Domain 8, Software Development Security. Expect questions mapping security tasks to development phases and comparing models such as waterfall, agile, and DevSecOps.