threat-modeling

threat-modeling is a skill for Claude Code from cbrock84/headcount. It costs 85 tokens per session (744 once invoked), scanned A, original, MIT.

A threat-modeling guide for identifying how a system could be attacked before it is built or changed. Threat modeling maps valuable assets, entry points, trust boundaries, and protections.

In plain words
What is it for?
It helps map data flows, identify trust boundaries, examine threats such as impersonation or data leaks, and choose controls for realistic risks.
Why use it?
It finds design-level security problems while they are still relatively cheap to fix, instead of after launch.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the security plugin — 8 skills shipped together

Good fit It helps map data flows, identify trust boundaries, examine threats such as impersonation or data leaks, and choose controls for realistic risks.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/cbrock84/headcount/threat-modeling
About the project

headcount is an organization of independently installable Claude Code plugins, each grouping skills for a department such as finance, security, or demand generation. Claude Code users install the departments they need and invoke their skills for specialized work; the catalogue entries are skills and related agent tooling from that organization.

cbrock84/headcount · 2,077 stars · on GitHub · cbrock84.github.io

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add cbrock84/headcount --skill threat-modeling
Clone the repo
git clone --depth 1 https://github.com/cbrock84/headcount

Made for: Claude Code.

Or install security, the plugin that ships this one along with the rest of its 8 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for threat-modeling

README.md
[![agentmods](https://agentmods.dev/badge/skills/cbrock84/headcount/threat-modeling/github.svg)](https://agentmods.dev/skills/cbrock84/headcount/threat-modeling)
Your own site
<a href="https://agentmods.dev/skills/cbrock84/headcount/threat-modeling"><img src="https://agentmods.dev/badge/skills/cbrock84/headcount/threat-modeling/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for threat-modeling

Your own site · 80×15
<a href="https://agentmods.dev/skills/cbrock84/headcount/threat-modeling"><img src="https://agentmods.dev/badge/skills/cbrock84/headcount/threat-modeling.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 85 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 744 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Excessive Agency · line 57
    Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.
    Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00085 $0.00744
Opus 5.5 $0.00034 $0.00298
Sonnet 5.5 $0.00017 $0.00149
Haiku 4.5 $0.00009 $0.00074

Measured 1mo ago against content hash cfd3dcfb8195, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

threat-modeling scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/security/skills/threat-modeling/SKILL.md · 65 lines

How it starts

The opening of the file, as written. The whole thing — 65 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Threat modeling

Done at design time this is cheap and changes the design. Done after launch it produces a list of things that are expensive to fix, so the timing is most of the value.

Four questions, in order

1. What are we building? A diagram of the actual data flow — not the org chart, not the marketing architecture. Components, the data moving between them, and where each store lives. If nobody can draw it, that is the first finding.

Mark the trust boundaries: every point where data crosses from something you control to something you do not, or from one privilege level to another. Almost every real vulnerability lives on a boundary.

2. What can go wrong? Walk each boundary and each asset. A usable prompt set:

  • Spoofing — can someone claim to be another user, service, or system?
  • Tampering — can data be modified in transit, at rest, or in the client?
  • Repudiation — can someone deny an action, and would we be able to show otherwise?
  • Information disclosure — what leaks: to other users, to logs, to error messages, to the client bundle?
  • Denial of service — what is unbounded? Uploads, queries, retries, fan-out.
  • Elevation of privilege — can a user reach data or actions belonging to another tenant, role, or account?

Two that catch more real bugs than the classic list: what does the client enforce that the server does not, and what happens on the second attempt — replay, race, and double-submit.

3. What are we going to do about it? For each realistic threat: mitigate, transfer, avoid, or accept. Accepting is legitimate; accepting silently is not.

Prioritize by attacker effort against impact, not by how alarming it sounds. A trivially exploitable tenant-isolation bug outranks a theoretical timing attack every time.

4. Did we do a good job? Re-check the model when the design changes. A threat model that describes last quarter's architecture is worse than none, because it produces false confidence.

Read the full file on GitHub · 65 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 1mo ago Changed · +7 lines cfd3dcfb8195
  2. 1mo ago First seen · 58 lines · 85 tokens per session scan A feecef10d70c

Subscribe to this mod's changes

threat-modeling is a skill published in the GitHub repository cbrock84/headcount (2,077 stars, last pushed 2d ago), licensed MIT. It adds 85 tokens to every session and 744 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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