security

A security-design guide for planning or reviewing protections such as login, permissions, input checks, secrets, and third-party libraries. Threat modeling means identifying who could attack a system, what they could target, and where its trust boundaries are.

In plain words
What is it for?
Use it when designing authentication, reviewing access controls, deciding how to handle secrets, checking dependencies, or planning defenses for a new system.
Why use it?
It helps find security risks and fit new decisions into the project’s existing security setup before implementation.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/hautc-it/cil/security
Any agent
npx skills add hautc-it/cil --skill security
Clone the repo
git clone --depth 1 https://github.com/hautc-it/cil

Made for: Claude Code, Codex.

Per session 59 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,058 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00059 $0.01058
Opus 5 $0.00030 $0.00529
Sonnet 5 $0.00012 $0.00212
Haiku 4.5 $0.00006 $0.00106

Measured yesterday against content hash fdffada484a4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

security 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 yesterday.

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.

templates/skills/security/SKILL.md · 89 lines

How it starts

The opening of the file, as written. The whole thing — 89 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Security Design Skill

Project Context

Existing project

  1. Read CLAUDE.md — security rules, compliance requirements, or auth decisions already made take priority.
  2. Check the existing auth system — read the auth middleware, session/token handling, and permission checks already in place. Extend the existing pattern — never introduce a parallel auth mechanism.
  3. Check secret management — how does this project load secrets (env vars, vault, config file)? Match that approach; never add a new secret-loading method.
  4. Check dependency manifest — understand what security-relevant libraries are already in use (auth libraries, crypto, validators).
  5. Search memorymemory_search("security auth [project] decision") — retrieve prior threat model decisions or known constraints.
  6. Improving security incrementally within the existing posture is safer than replacing it wholesale.

Greenfield project

Security is cheapest to build in from the start — retrofitting it is expensive and error-prone:

  1. Do the threat model before writing any auth code — answer: who are the actors, what are the assets, where are the trust boundaries, what are the realistic attack vectors. Write the answers down; they become the security spec.
  2. Choose auth approach once — stateless token (no server state, harder to revoke) vs session (server state, easy revoke) vs platform credential (mobile/desktop keychain, OS identity). Pick based on deployment model and revocation requirements. Document it.
  3. Set secret management from day one — environment variables as the minimum floor; a dedicated secrets store for any cloud or team deployment. Never commit credentials, connection strings, or API keys.
  4. Define input validation strategy — validate at the boundary (API entry, UI input, file import), not deep inside business logic. Pick one validation approach and use it everywhere.
  5. Add dependency auditing to the build pipeline — use the standard audit tool for the platform. Integrate it from the first CI run; bolt-on tooling after 100 dependencies is painful.
  6. Write security decisions into CLAUDE.md — auth approach, token lifetimes, where secrets live, validation approach. Makes them explicit and non-negotiable for all contributors.
  7. Store the decisions:
    memory_store("decision", "security: auth=[x], secrets=[x], validation=[x], dependency audit=[x]", ["security", "auth", "conventions"])
    

Read the full file on GitHub · 89 lines

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. yesterday First seen · 89 lines · 59 tokens per session scan A fdffada484a4

Subscribe to this mod's changes

security is a skill published in the GitHub repository hautc-it/cil (1 stars, last pushed 1mo ago), licensed MIT. It adds 59 tokens to every session and 1,058 once invoked, about $0.0003 per session on Opus 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 2026-08-31.