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Agent skill

Threat Modeling

by cbrock84 in cbrock84/headcount

Identifies what could go wrong in a system before it is built or changed — the assets worth attacking, the entry points, the trust boundaries, and the controls that actually address the realistic…

MITAuto-check passedSecurity

Install Threat Modeling

skills CLI
$ npx skills add cbrock84/headcount --skill threat-modeling -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install cbrock84/headcount threat-modeling --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/cbrock84/headcount.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/security/skills/threat-modeling .claude/skills/threat-modeling && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
threat-modeling
GitHub stars
2k
Token cost
~841 tokens
SKILL.md length
468 words
Files
2 (incl. references)
Skills in repo
178
Repo updated
First seen
Licence
MIT

At a glance

Identifies what could go wrong in a system before it is built or changed — the assets worth attacking, the entry points, the trust boundaries, and the controls that actually address the realistic…

  • Tasks that involve Threat modeling
  • SKILL.md covers Four questions, in order, Scoping, Sources and Never
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
  • Tasks that involve Security review

What it does

Threat Modeling is an agent skill from cbrock84/headcount. Identifies what could go wrong in a system before it is built or changed — the assets worth attacking, the entry points, the trust boundaries, and the controls that actually address the realistic threats. Use this when designing a feature or system, when a change touches authentication, data handling, payments, or external input, before a security review, or when deciding which security work is worth doing at all.

Its SKILL.md is about 840 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/sources.md`).

It sits in Security, covering Threat modeling and Security review. The repository describes itself as: An agent organization structured as a company — 15+ departments, 125+ skills, each independently installable, citing the standards and regulators that settle the question. Runs… The licence is MIT.

When your agent uses it

  • Tasks that involve Threat modeling
  • Tasks that involve Security review

Example prompts

  • “Use the threat-modeling skill to identify what could go wrong in a system before it is built or changed — the assets worth attacking, the entry…”
  • “/threat-modeling”

What it can do on your machine

Read from SKILL.md and the folder at commit 98d1c17. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Threat Modeling loads about 841 tokens when it runs, and up to ~1.1k if it reads all its reference files. Until then it costs about 108 tokens; SKILL.md has 468 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~108
When it runs · the whole SKILL.md, loaded when a task matches
~841
With references · SKILL.md plus every file in references/, read only if the agent opens them
~1.1k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from cbrock84/headcount at commit 98d1c17, republished under its MIT licence (© cbrock84). 468 words, ~841 tokens.

Download SKILL.mdSave it as .claude/skills/threat-modeling/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.
name
threat-modeling
description
Identifies what could go wrong in a system before it is built or changed — the assets worth attacking, the entry points, the trust boundaries, and the controls that actually address the realistic threats. Use this when designing a feature or system, when a change touches authentication, data handling, payments, or external input, before a security review, or when deciding which security work is worth doing at all.

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.

Show full SKILL.md (148 more words)Show less

Scoping

Model per feature or per boundary, not per system. A whole-system model is too big to finish and too vague to act on.

Timebox it. An hour on a specific feature with the engineers who will build it beats a week-long exercise producing a document nobody reads.

Sources

references/sources.md in this skill lists the outside authorities that settle the questions here — what each one is authoritative for, and what you may do with it. Check them before answering on anything they cover, and cite what you used. Most are free to read and not free to reproduce; the use note on each is binding.

Never

  • Model the system as designed rather than as built. Ask what actually got shipped.
  • Assume internal traffic is trusted. That assumption is what turns one compromised service into an incident.
  • Accept "the framework handles that" without checking that it is configured to.

© cbrock84, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file (references) in plugins/security/skills/threat-modeling of cbrock84/headcount.

  • SKILL.md
  • references/sources.md

Open the folder on GitHubat commit 98d1c17

Compare with similar skills

Threat Modeling next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Threat Modeling compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Threat Modeling this skillcbrock84/headcount2k—~841Automated safety check: PassMIT
Commit Security Scancodexstar69/bug-hunter519—~629Automated safety check: PassMIT
Auditing Code For Vulnerabilitiestrilwu/secskills157—~3.2kAutomated safety check: PassMIT
Threat Mitigation Mappingwshobson/agents40k8 repos~742Automated safety check: PassMIT
Audit Browser Security Boundariesnordstjernen-web/northstar-browser124—~920Automated safety check: PassGPL-3.0
Security Auditblueberrycongee/termcanvas406—~966Automated safety check: NotesMIT

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Categories

Questions about Threat Modeling

What does Threat Modeling do?

Identifies what could go wrong in a system before it is built or changed — the assets worth attacking, the entry points, the trust boundaries, and the controls that actually address the realistic…. Threat Modeling is an agent skill from cbrock84/headcount. Identifies what could go wrong in a system before it is built or changed — the assets worth attacking, the entry points, the trust boundaries, and the controls that actually address the realistic threats.

When should I use Threat Modeling?

Threat Modeling fits situations like: tasks that involve Threat modeling; tasks that involve Security review.

How do I install Threat Modeling in Claude Code?

Run `npx skills add cbrock84/headcount --skill threat-modeling -a claude-code`. Or copy the skill folder (plugins/security/skills/threat-modeling in cbrock84/headcount) into .claude/skills/threat-modeling in your project. Claude Code loads it when a task matches its description.

How do I install Threat Modeling in Codex?

Run `npx skills add cbrock84/headcount --skill threat-modeling -a codex`. Or copy the skill folder (plugins/security/skills/threat-modeling in cbrock84/headcount) into .agents/skills/threat-modeling in your project. Codex loads it when a task matches its description.

Can I use Threat Modeling in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add cbrock84/headcount --skill threat-modeling -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/threat-modeling, .gemini/skills/threat-modeling, .github/skills/threat-modeling and .opencode/skills/threat-modeling in your project.

What does Threat Modeling need to run?

SKILL.md names no scripts, command-line tools or credentials: Threat Modeling is instructions for the agent only.

Does Threat Modeling access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Threat Modeling safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Threat Modeling use?

Threat Modeling is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Threat Modeling use?

About 841 tokens (SKILL.md is roughly 3.4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 300 tokens, read only when the agent opens those files.

What are the alternatives to Threat Modeling?

Skills that share tags, products or a category with Threat Modeling: Commit Security Scan (codexstar69/bug-hunter, 519 stars), Auditing Code For Vulnerabilities (trilwu/secskills, 157 stars), Threat Mitigation Mapping (wshobson/agents, 40k stars) and Audit Browser Security Boundaries (nordstjernen-web/northstar-browser, 124 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Threat Modeling?

cbrock84 (a GitHub user) maintains it in cbrock84/headcount, which has 2,016 GitHub stars. The repository holds 178 skills in this directory. The repository was last updated on September 17, 2026.

Source: cbrock84/headcount on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.