secure-by-design

secure-by-design is a skill for Claude Code, Codex from ooiyeefei/ccc. It costs 143 tokens per session (1,399 once invoked), scanned A, original, MIT.

A security review guide for system designs and existing code. It evaluates what needs protection, how trust boundaries work, and which access controls fit the system and team.

In plain words
What is it for?
Use it to review authentication, role-based access, multi-tenant systems, APIs, and agents. It can help design permissions, audit logging, least-privilege access, and protections against unauthorized resource access.
Why use it?
It replaces broad security checklists with a short, prioritized set of controls tied to actual risks. It helps identify unsafe permission, authentication, audit, and multi-tenant design choices before release.

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/ooiyeefei/ccc/secure-by-design
Any agent
npx skills add ooiyeefei/ccc --skill secure-by-design
Clone the repo
git clone --depth 1 https://github.com/ooiyeefei/ccc

Made for: Claude Code, Codex.

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 secure-by-design

README.md
[![agentmods](https://agentmods.dev/badge/skills/ooiyeefei/ccc/secure-by-design.svg)](https://agentmods.dev/skills/ooiyeefei/ccc/secure-by-design)
Your own site
<a href="https://agentmods.dev/skills/ooiyeefei/ccc/secure-by-design"><img src="https://agentmods.dev/badge/skills/ooiyeefei/ccc/secure-by-design.svg" alt="Measured on agentmods" height="20"></a>
Per session 143 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,399 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 5.1 $0.00143 $0.01399
Opus 5 $0.00072 $0.00700
Sonnet 5 $0.00029 $0.00280
Haiku 4.5 $0.00014 $0.00140

Measured 6d ago against content hash cbab6c5fb24f, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

secure-by-design 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 6d 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.

skills/secure-by-design/SKILL.md · 64 lines

How it starts

The opening of the file, as written. The whole thing — 64 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Secure by design

A review partner for the security of any system — an RBAC model, a multi-tenant SaaS, an API, an agent. You classify what you are protecting before proposing controls, then recommend only what fits the assets, trust boundaries, and team scale. Output: a short, ranked list of applicable controls with the reasoning, not a generic checklist dump.

The leading words below are load-bearing. Use them in your reasoning — they carry the decisions.

Leading words (say these)

  • deny-by-default — an unmapped permission is denied, never allowed.
  • fail-closed — unknown state ⇒ deny; an error path never grants access.
  • least privilege — the smallest capability that does the job; unknown/absent role ⇒ the least-privileged role.
  • two axes (scope × role)which resources vs what actions are independent; do not collapse siblings onto one ladder.
  • anti-IDOR — never trust a client-supplied id as a grant; resolve the caller's own scope independently.
  • append-only audit — one immutable event per privileged action, in the same transaction, actor bound from auth (never a client arg).
  • eligible-not-active (JIT) — sensitive access is requested → approved → activated → auto-expires; default OFF.
  • four-eyes — critical actions are proposed by one person and executed only after a different person approves (separation of duties: requester ≠ approver).
  • blast radius — how much one compromised credential or mistake can touch; minimize it.
  • data minimization — mask/omit sensitive data below the role that needs it; expose aggregates, not raw PII.
  • deploy-authority separation — only CI holds the deploy key; humans and feature branches cannot deploy.
  • break-glass — a documented, logged, reviewed-after emergency bypass.
  • bones now, ceremony later — build the primitives into the schema early; defer the process overhead.

The review (do these in order — do NOT jump to controls)

Legwork first. The most common failure is proposing controls before understanding what is protected. Complete steps 1–2 fully before step 3.

Read the full file on GitHub · 64 lines

Files

What ships with it

5 files 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. 6d ago First seen · 64 lines · 143 tokens per session scan A cbab6c5fb24f

Subscribe to this mod's changes

secure-by-design is a skill published in the GitHub repository ooiyeefei/ccc (484 stars, last pushed 1mo ago), licensed MIT. It adds 143 tokens to every session and 1,399 once invoked, about $0.0007 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 2026-08-30.

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