Secure Software Development Lifecycle
Security in every phase
Defects are cheapest to fix in the phase that created them and most expensive in production. Security must therefore be present from requirements onward, not bolted on before release.
- Requirements — define security requirements and privacy needs; classify the data involved.
- Design — threat modelling (STRIDE), attack surface reduction, secure design review.
- Development — secure coding standards, peer review, static analysis.
- Testing — dynamic analysis, fuzzing, penetration testing, misuse cases.
- Deployment and maintenance — hardened configuration, change control, patching, decommissioning.
Development models
- Waterfall — sequential, hard to revisit earlier phases.
- Spiral — iterative with explicit risk analysis each cycle.
- Agile / Scrum — short iterations; security must be built into the definition of done.
- DevSecOps — automated security gates in the CI/CD pipeline.
- Maturity models: CMMI levels and the Software Assurance Maturity Model.
Change control
A formal change control process — request, impact analysis, approval, testing, documented implementation, and rollback plan — is what keeps a secure build secure over time.