Threat Modeling Fundamentals — DevSecOps Interactive Learning

What is threat modeling?

Threat modeling is a disciplined method to identify, quantify, and address security risks in a system. You capture how the system works (data flows, trust boundaries), enumerate threats, prioritize mitigations, and track residual risk. It turns vague worry into actionable work items for architects, developers, and operations.

Four-step process

Most lightweight approaches follow this loop—click each step for a quick prompt you can use in workshops.

1. Diagram

Draw data flows, actors, and trust boundaries.

2. Identify

Use STRIDE, misuse cases, or attack libraries.

3. Mitigate

Controls, design changes, monitoring.

4. Validate

Test assumptions; update as architecture changes.

Why it matters in DevSecOps

Shift-left design flaws: Catch authentication gaps and trust-boundary mistakes before code is written.
Pipeline alignment: Threat findings become security user stories, abuse cases, and automated checks.
Shared language: Product, engineering, and security prioritize the same risks with evidence.
Continuous updates: Re-model on major feature or architecture changes—living artifact, not shelfware.

Tools (comparison)

Tool / style	Best for	Notes
Microsoft Threat Modeling Tool	Data-flow + STRIDE	Windows-centric
OWASP Threat Dragon	Web apps, diagrams in Git	Open source
iriusRisk / enterprise TM	Scaled programs, risk registers	Commercial
Whiteboard + STRIDE	Fast iteration	No license

Banking use case

Mobile banking API modernization

Context: A bank exposes account aggregation and payment initiation APIs to a new mobile app and partner fintechs.

Diagram: Trust boundaries between mobile device, API gateway, core banking, and fraud engine.

Threats: Token theft (spoofing), transaction repudiation, rate-limit bypass (DoS), insecure deserialization to core systems.

Mitigations: mTLS or OAuth2 with binding, step-up auth for high-risk payments, WAF + bot management, strict schema validation, centralized audit.

Outcome: Security requirements feed API design reviews and CI policy tests (schema, auth scopes, PII tagging).