secure-software-engineering
Secure Software Engineering
Build security into decisions before defects reach production. This is a prevention-oriented workflow, not a claim that a design or release is secure. Record assumptions, the evidence collected, residual risks, and the owner of any accepted exception.
When To Use
Use this skill to answer "How do we build this securely?" for a new feature, integration, service, API, tenant boundary, AI capability, or release. Start early and revisit affected decisions when architecture, data flows, dependencies, or threats change.
Do not use it for an authorized post-build assessment: use security-audit-methodology. Do not use it as a vulnerability scanner for an existing codebase; use an authorized scanning tool or specialist security assessment. Use spec-driven-development when the task is to formalize the resulting requirements and phase gates, and verification-methodology to make evidence-backed completion claims.
Workflow
- Requirements: identify assets, actors, harm, data classifications, regulatory or contractual constraints, and security outcomes. Write testable acceptance criteria before selecting controls.
- Threat model: map data flows and trust boundaries; state assumptions, abuse cases, mitigations, and residual risk. STRIDE is optional vocabulary, not an exhaustive method.
- Design: choose controls that fit the trust model, including server-side authorization, data isolation, safe failure behavior, and AI capability boundaries. Explain rejected alternatives.
- Implement: make each boundary enforceable in code and configuration; protect input, output, credentials, dependencies, logs, and operational paths.
- Review and release: verify controls with direct evidence, review changes for bypasses, preserve release evidence, and feed incidents or near misses into requirements and tests.
Loop to the affected phase when evidence contradicts an assumption or a design changes. Stop when each material decision has an accountable owner, direct evidence or an explicit gap, and a disposition for residual risk.