skill_id: SEC-THREAT-MODELING version: 1.0.0 last_updated: 2026-01-04 applies_to: [Class A, Class B, Class C] jurisdiction: [Global] prerequisites: [REG-ISO14971]
Threat Modeling for Medical Devices
Purpose
Identify, prioritize, and mitigate security threats for medical devices, integrating with risk management and informing control selection.
When to Apply
- New features, interfaces, protocols, or deployment models.
- Architectural changes or introduction of third-party components.
- Periodic review or after security incidents.
Requirements (testable)
- Scope & Assets: Define assets (PHI, credentials, control channels) and trust boundaries. Rationale: focus analysis.
- Methodology: Apply STRIDE (or equivalent) to data flows/components; document threats and mitigations. Rationale: structured coverage.
- Prioritization: Rate threats by likelihood/impact; align with risk criteria; focus on high/critical. Rationale: actionable output.
- Controls Mapping: Map threats to controls (auth, crypto, logging, rate limits, updates); ensure ownership and implementation path. Rationale: closure.
- Validation: Include verification activities (tests, pen/DAST/fuzz) for high-risk threats. Rationale: evidence of mitigation.
- Update & Trace: Update threat model on changes; keep versioned; link to requirements and tests. Rationale: current and auditable.
Recommended Practices
- Use DFDs to visualize flows; include physical ports and debug interfaces.
- Consider safety impacts of security failures (link to ISO 14971 hazards).
- Capture abuse cases (e.g., radio flooding, spoofing, replay).
- Keep a concise threat model summary with top risks for quick consumption.
Patterns
Threat entry (YAML):
# REQ-THM-01
threat_id: TH-07
component: BLE Control Service
stride: Spoofing
description: Attacker pairs via Just Works and sends control commands.
mitigations:
- REQ-BLE-SEC-01 (LESC + MITM)
- REQ-AUTH-RBAC-03 (role checks)
verification:
- TEST-BLE-05 (pairing)
- PEN-02 (spoof attempt)
DFD elements:
External: Clinician App
Process: Device Control Task
Data Store: Config Flash (encrypted)
Boundary: BLE link (encrypted/authenticated)
Anti-Patterns (risks)
- No threat model or outdated one -> risk: missed controls, audit finding.
- Listing threats without mapping to controls -> risk: no mitigation.
- Ignoring verification -> risk: unproven controls.
- Not updating after major change -> risk: stale mitigations.
Verification Checklist
- Assets and trust boundaries defined; DFDs updated.
- STRIDE (or equivalent) applied to components/flows.
- High/critical threats prioritized with rationale.
- Threats mapped to implemented controls; owners assigned.
- Verification (tests/pen/fuzz) planned/executed for high risks.
- Threat model versioned and updated after changes.
Traceability
- Threat IDs (
TH-###) linked to controls (REQ-###/RISK-CTRL-###) and tests (TEST-###,PEN-###,FUZZ-###). - Store threat model artifacts with release; reference in risk management file.
References
- STRIDE (Microsoft), attack surface reduction concepts.
- FDA Cybersecurity Premarket Guidance (threat modeling).
- IEC 62443 threat concepts (zones/conduits).
Changelog
- 1.0.0 (2026-01-04): Initial threat modeling skill with STRIDE application, control mapping, and verification linkage.
Audit History
- 2026-01-04: Audit performed. Verified:
- STRIDE methodology correctly attributed to Microsoft
- DFD-based threat modeling approach accurately described
- Integration with FDA cybersecurity guidance correctly noted