How do I install the Threat Modeler skill?

Run npx skillmds@latest add willianbs/threat-modeler in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Threat Modeler safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Threat Modeler?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Threat Modeler free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Threat Modeler?

willianbs (@willianbs) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Threat Modeler by willianbs — Agent Skill

Name: Threat Modeler
Author: willianbs

Threat Modeler

Builds asset- and STRIDE-based threat models before deep security audits. Use for new features touching auth, data, trust boundaries, or HighRisk specs. Emits THREAT_MODEL. Never invents exploits or replaces security-auditor findings.

willianbs 25cfe9a 2 files · 4.2 KB Updated Sep 17, 2026

File contents

Purpose

Produce a structured threat model (assets, trust boundaries, STRIDE abuse cases, prioritized threats) that security-auditor and delivery-planner can consume.

When to Use / When NOT to Use

Use when: new HighRisk features; auth/PII/payments/integrations; before security-auditor on greenfield surfaces; architecture changes that move trust boundaries.

Do not use when: style-only PRs; trivial chores; full vuln hunting (security-auditor); active exploit response without modeling first is OK to skip lite.

Preconditions

Scope (feature/system) and enough CONTEXT_PACK to identify actors, data, and boundaries. If missing, ask before inventing assets.

Inputs / Outputs

Inputs: feature/system scope, CONTEXT_PACK, SPEC_STATUS (preferred), data classification if known.

Outputs: THREAT_MODEL

Upstream / Downstream

Upstream: context-loader, spec-validator, delivery-planner, engineering-os.

Downstream: security-auditor, delivery-planner, adr-enforcer, test-strategy-designer.

Core Principles

Assets and trust boundaries before checklists.
STRIDE-light: Spoofing, Tampering, Repudiation, Info disclosure, DoS, Elevation.
Threats need actor + asset + abuse path.
Prioritize by Likelihood × Impact; mark assumptions.
Feed security-auditor — do not duplicate deep code audit.
Redact secrets; never invent CVEs.
Unknown boundaries → ProceedWithConditions, not fake completeness.

Process

Lite

Single feature / small API: list assets, 2–4 trust boundaries, top STRIDE threats, hand off.

Full

Actors — users, admins, services, attackers, insiders.
Assets — data, secrets, sessions, money, admin actions, reputation.
Diagram (textual) — components and trust boundaries.
STRIDE pass per boundary/asset.
Threat list — ID, description, likelihood, impact, severity, mitigations (existing vs needed).
Out of scope — explicitly list.
Decision: Proceed to security-auditor / Revise design / Block if Critical unmitigated design flaw.

Evidence Requirements

Cite real modules/APIs from CONTEXT_PACK. Label assumptions. No invented endpoints.

Stop Conditions / Failure Modes

Condition	Action
Cannot identify assets/boundaries	Ask; Block if HighRisk
Design has Critical unmitigated threat	Block until design change or accepted risk
Scope is pure UI copy	Refuse; not applicable

Severity + Confidence

Threat severity uses portfolio standard. Critical = auth bypass / mass data exposure / RCE-class design flaws.

Output Contract

## THREAT_MODEL
Scope: ...
Actors: ...
Assets: ...
Trust boundaries: ...
Threats:
  - ID, STRIDE, severity, likelihood, impact, mitigations
Assumptions: ...
Decision: Proceed | ProceedWithConditions | Revise | Block

Handoffs

security-auditor (primary), adr-enforcer (security architecture), test-strategy-designer (negative cases), delivery-planner (mitigation tasks).

Never

Never invent vulnerabilities in code you did not reason about.
Never print secrets.
Never replace security-auditor with a shallow STRIDE table alone for ship decisions.
Never skip assets/boundaries and jump to OWASP laundry lists.

---name: threat-modelerdescription: Builds asset- and STRIDE-based threat models before deep security audits. Use for new features touching auth, data, trust boundaries, or HighRisk specs. Emits THREAT_MODEL. Never invents exploits or replaces security-auditor findings.---# PurposeProduce a structured threat model (assets, trust boundaries, STRIDE abuse cases, prioritized threats) that security-auditor and delivery-planner can consume.# When to Use / When NOT to Use**Use when:** new HighRisk features; auth/PII/payments/integrations; before security-auditor on greenfield surfaces; architecture changes that move trust boundaries.**Do not use when:** style-only PRs; trivial chores; full vuln hunting (security-auditor); active exploit response without modeling first is OK to skip lite.# PreconditionsScope (feature/system) and enough CONTEXT_PACK to identify actors, data, and boundaries. If missing, ask before inventing assets.# Inputs / Outputs**Inputs:** feature/system scope, CONTEXT_PACK, SPEC_STATUS (preferred), data classification if known.**Outputs:** `THREAT_MODEL`# Upstream / Downstream**Upstream:** context-loader, spec-validator, delivery-planner, engineering-os.**Downstream:** security-auditor, delivery-planner, adr-enforcer, test-strategy-designer.# Core Principles1. Assets and trust boundaries before checklists.2. STRIDE-light: Spoofing, Tampering, Repudiation, Info disclosure, DoS, Elevation.3. Threats need actor + asset + abuse path.4. Prioritize by Likelihood × Impact; mark assumptions.5. Feed security-auditor — do not duplicate deep code audit.6. Redact secrets; never invent CVEs.7. Unknown boundaries → ProceedWithConditions, not fake completeness.# Process## LiteSingle feature / small API: list assets, 2–4 trust boundaries, top STRIDE threats, hand off.## Full1. **Actors** — users, admins, services, attackers, insiders.2. **Assets** — data, secrets, sessions, money, admin actions, reputation.3. **Diagram (textual)** — components and trust boundaries.4. **STRIDE pass** per boundary/asset.5. **Threat list** — ID, description, likelihood, impact, severity, mitigations (existing vs needed).6. **Out of scope** — explicitly list.7. Decision: Proceed to security-auditor / Revise design / Block if Critical unmitigated design flaw.# Evidence RequirementsCite real modules/APIs from CONTEXT_PACK. Label assumptions. No invented endpoints.# Stop Conditions / Failure Modes| Condition | Action ||-----------|--------|| Cannot identify assets/boundaries | Ask; Block if HighRisk || Design has Critical unmitigated threat | Block until design change or accepted risk || Scope is pure UI copy | Refuse; not applicable |# Severity + ConfidenceThreat severity uses portfolio standard. Critical = auth bypass / mass data exposure / RCE-class design flaws.# Output Contract```## THREAT_MODELScope: ...Actors: ...Assets: ...Trust boundaries: ...Threats: - ID, STRIDE, severity, likelihood, impact, mitigationsAssumptions: ...Decision: Proceed | ProceedWithConditions | Revise | Block```# Handoffs**security-auditor** (primary), **adr-enforcer** (security architecture), **test-strategy-designer** (negative cases), **delivery-planner** (mitigation tasks).# Never- Never invent vulnerabilities in code you did not reason about.- Never print secrets.- Never replace security-auditor with a shallow STRIDE table alone for ship decisions.- Never skip assets/boundaries and jump to OWASP laundry lists.

Frequently asked questions