aws-s3-security

aws-s3-security is a skill for Claude Code, Codex from HermeticOrmus/LibreSecOps-Claude-Code. It costs 0 tokens per session (1,971 once invoked), scanned A, original, MIT.

A guide to securing Amazon S3, AWS's service for storing files and data. It explains how account settings, bucket policies, permissions, access points, and encryption work together.

In plain words
What is it for?
Use it to review Block Public Access, bucket policies, legacy ACLs, IAM permissions, access points, object ownership, and encryption settings.
Why use it?
It helps prevent accidental public access and other mistakes caused by overlapping S3 access controls.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to review Block Public Access, bucket policies, legacy ACLs, IAM permissions, access points, object ownership, and encryption settings.

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Install with agentmods
npx agentmods add skills/hermeticormus/libresecops-claude-code/aws-s3-security
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 HermeticOrmus/LibreSecOps-Claude-Code --skill aws-s3-security
Clone the repo
git clone --depth 1 https://github.com/HermeticOrmus/LibreSecOps-Claude-Code

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.

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README.md
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Your own site
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agentmods 80×15 button for aws-s3-security

Your own site · 80×15
<a href="https://agentmods.dev/skills/hermeticormus/libresecops-claude-code/aws-s3-security"><img src="https://agentmods.dev/badge/skills/hermeticormus/libresecops-claude-code/aws-s3-security.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,971 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.
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 $0.00000 $0.01971
Opus 5 $0.00000 $0.00986
Sonnet 5 $0.00000 $0.00394
Haiku 4.5 $0.00000 $0.00197

Measured 8d ago against content hash 28f75589a065, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

aws-s3-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 8d 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/cloud-security-aws/skills/aws-s3-security/SKILL.md · 219 lines

How it starts

The opening of the file, as written. The whole thing — 219 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AWS S3 Security

S3 bucket security configurations, access control models, encryption patterns, and data exposure prevention.

Knowledge Base

S3 Access Control Layers

S3 has multiple overlapping access control mechanisms. Understanding the hierarchy prevents misconfigurations:

  1. Block Public Access (Account level) -- Master switch. If enabled at account level, overrides all bucket-level settings. This is your first line of defense.
  2. Block Public Access (Bucket level) -- Per-bucket controls. Four independent settings:
    • BlockPublicAcls -- Rejects PUT requests with public ACLs
    • IgnorePublicAcls -- Ignores existing public ACLs
    • BlockPublicPolicy -- Rejects bucket policies that grant public access
    • RestrictPublicBuckets -- Restricts access to bucket with public policies to AWS principals only
  3. Bucket Policy -- JSON policies attached to the bucket. Most flexible control.
  4. ACLs (Legacy) -- Predates bucket policies. AWS recommends disabling ACLs entirely (S3 Object Ownership set to "Bucket owner enforced").
  5. IAM Policies -- Control what IAM principals can do with S3.
  6. Access Points -- Named network endpoints with their own access policies, scoped to specific prefixes.
  7. VPC Endpoint Policies -- Control which buckets can be accessed from a VPC endpoint.

S3 Encryption Models

Type Key Description Use Case
SSE-S3 AWS managed, auto-rotated S3 manages everything Default encryption, no key management overhead
SSE-KMS Customer managed or AWS managed KMS key Separate key management, audit trail via CloudTrail When you need key rotation control, access auditing, or cross-account key sharing
SSE-C Customer provided per request Customer sends key with each request Regulatory requirement to hold keys outside AWS
Client-side Customer managed entirely Encrypt before upload Zero-trust of AWS, end-to-end encryption

Default recommendation: SSE-KMS with a customer-managed key. It provides the best balance of security, auditability, and operational simplicity.

Read the full file on GitHub · 219 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. 8d ago First seen · 219 lines · 0 tokens per session scan A 28f75589a065

Subscribe to this mod's changes

aws-s3-security is a skill published in the GitHub repository HermeticOrmus/LibreSecOps-Claude-Code (4 stars, last pushed 3mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,971 tokens. 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.

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