Threat Modeling (STRIDE)

Workflow

1. Scope — Identify the system boundary, assets (PII, credentials, payments), and availability requirements (SLO/SLA).
2. Data Flow Diagram — Map actors, entry points, data stores, and external dependencies. Mark trust boundaries (public internet → edge → internal → database → third-party).
3. STRIDE per element — For each element in the diagram, walk through all six STRIDE categories (Spoofing, Tampering, Repudiation, Information disclosure, Denial of service, Elevation of privilege) and record threats.
4. Risk score — Rate each threat by Impact (Low/Med/High) and Likelihood (Low/Med/High). Prioritize High-impact + Med/High-likelihood items first.
5. Mitigate — Convert each prioritized threat into engineering tasks, verification tasks (tests, alerts), and operational controls (runbooks, access reviews).
6. Tickets and tests — Create backlog items for mitigations and add abuse-case tests for critical flows. Add PR checklist items for ongoing verification.

Example: Threat Register Row

This single row drives three artifacts: an engineering ticket (implement revocation-list middleware), a test (verify revoked token returns 401 within TTL window), and a PR checklist item (authz checks for new endpoints).

Validation Checkpoint

Before finalizing, verify completeness:

• Every element in the data flow diagram has at least one STRIDE entry
• All High-impact threats have an assigned owner and mitigation
• Each mitigation maps to a backlog ticket or test case
• Threat model doc includes assumptions and scope boundaries
• PR checklist updated with new security requirements

Outputs (Definition of Done)

Produce a data flow diagram, a threat register, and a mitigation plan that becomes tickets and tests.

Load Next (References)

• references/stride-workshop.md — step-by-step workshop agenda + DFD guidance
• references/common-threats-and-mitigations.md — threat catalog with mitigations
• references/templates.md — copy/paste templates for docs and tickets