Threat modeler

AI Engineering Operating System

Install

npx -y skills add willianbs/skills --skill threat-modeler

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

2 things to look at

19 days oldThe repository was created 19 days ago. New is not bad, but a brand new repository carrying a familiar-sounding name is the shape a typosquat arrives in, and there has been no time for anyone else to find a problem with it.
0 stars0 stars. Stars are a popularity signal and not a quality one, but at this level it is likely that nobody has read this closely except its author, and you would be relying on your own review.

What its author says it does

Copied from the file, not written here

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.

SKILL.md

3.5 KB, as published. Nobody here has run it

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.