Threat Model Skill

STRIDE threat modeling for secure design.

Workflow

1. Define scope: What system/feature/component is being modeled?

2. Draw data flow diagram (textual):

   • Identify actors (users, external systems)
   • Identify processes (services, functions)
   • Identify data stores (databases, caches, files)
   • Identify data flows (what moves between components)
   • Identify trust boundaries (where trust level changes)

3. For each component and data flow, assess STRIDE threats:

   Threat	Description	Question to Ask
   Spoofing	Impersonating something or someone	Can an attacker pretend to be this user/system?
   Tampering	Modifying data or code	Can data be changed in transit or at rest?
   Repudiation	Claiming to not have done something	Can a user deny an action without accountability?
   Info Disclosure	Exposing data to unauthorized parties	Can sensitive data leak?
   Denial of Service	Making the system unavailable	Can this component be overwhelmed?
   Elevation of Privilege	Gaining unauthorized access	Can a user escalate their permissions?

4. For each identified threat:

   • Severity: Critical / High / Medium / Low
   • Likelihood: High / Medium / Low
   • Existing mitigations (if any)
   • Recommended mitigations
   • Residual risk after mitigation

   For AI-powered systems: Extend STRIDE with AI-specific threat dimensions:

   • Autonomy risk: Can the AI take actions beyond its intended scope?
   • Oversight gap: Is human-in-the-loop oversight meaningful? (Test Authority/Time/Understanding per Bannerman's triad -- see security-trust.md)
   • Feedback poisoning: Can adversarial inputs degrade the system over time?
   • Opacity risk: Can decisions be explained to affected parties?

5. Output:

   Copy

   ## Threat Model: [System/Feature]
   
   ### Data Flow
   [textual diagram]
   
   ### Trust Boundaries
   - [boundary 1]: [what changes]
   - [boundary 2]: [what changes]
   
   ### Threats
   | ID | Component | STRIDE | Threat | Severity | Likelihood | Mitigation |
   |----|-----------|--------|--------|----------|-----------|------------|
   | T1 | ... | S | ... | ... | ... | ... |
   
   ### Priority Actions
   1. [highest priority mitigation]
   2. [next priority]
   3. [next priority]
   

OWASP Top 10 for LLM Applications (2025)

For AI-powered products (product_type: ai_tool or any product using LLM components), extend the STRIDE analysis with LLM-specific threats:

Source: OWASP Top 10 for LLM Applications v2025.1 (genai.owasp.org). Updated from v1.1 (2023) — new entries: System Prompt Leakage (LLM07), Vector and Embedding Weaknesses (LLM08), Misinformation (LLM09), Unbounded Consumption (LLM10).

For each LLM component in the threat model, assess all 10 threats. Use alongside STRIDE — STRIDE covers system-level threats, OWASP LLM covers model-level threats.

Theory Citations

• STRIDE: Microsoft threat modeling methodology (Shostack)
• OWASP Top 10:2025: Web application security risks
• OWASP Top 10 for LLM Applications v2025: AI/LLM-specific security risks