analyzing-mach-o-binaries-on-macos

analyzing-mach-o-binaries-on-macos is a skill for Claude Code, Codex from meltedinhex/analyst-ai-pack. It costs 75 tokens per session (780 once invoked), scanned A, original, Apache-2.0.

A static-analysis guide for Mach-O files, the executable format used by macOS. It covers regular and universal binaries, linked libraries, permissions, and code-signing information.

In plain words
What is it for?
Use it to inspect macOS malware, compare architecture slices, review linked libraries and permissions, and check entry points and signatures.
Why use it?
It helps estimate what a macOS sample may do and whether it is signed or trusted, without running it on a real computer.

Skill for Claude CodeCodex

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

Good fit Use it to inspect macOS malware, compare architecture slices, review linked libraries and permissions, and check entry points and signatures.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/meltedinhex/analyst-ai-pack/analyzing-mach-o-binaries-on-macos
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 meltedinhex/analyst-ai-pack --skill analyzing-mach-o-binaries-on-macos
Clone the repo
git clone --depth 1 https://github.com/meltedinhex/analyst-ai-pack

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 analyzing-mach-o-binaries-on-macos

README.md
[![agentmods](https://agentmods.dev/badge/skills/meltedinhex/analyst-ai-pack/analyzing-mach-o-binaries-on-macos/github.svg)](https://agentmods.dev/skills/meltedinhex/analyst-ai-pack/analyzing-mach-o-binaries-on-macos)
Your own site
<a href="https://agentmods.dev/skills/meltedinhex/analyst-ai-pack/analyzing-mach-o-binaries-on-macos"><img src="https://agentmods.dev/badge/skills/meltedinhex/analyst-ai-pack/analyzing-mach-o-binaries-on-macos/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 analyzing-mach-o-binaries-on-macos

Your own site · 80×15
<a href="https://agentmods.dev/skills/meltedinhex/analyst-ai-pack/analyzing-mach-o-binaries-on-macos"><img src="https://agentmods.dev/badge/skills/meltedinhex/analyst-ai-pack/analyzing-mach-o-binaries-on-macos.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 75 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 780 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 $0.00075 $0.00780
Opus 5 $0.00037 $0.00390
Sonnet 5 $0.00015 $0.00156
Haiku 4.5 $0.00007 $0.00078

Measured 11d ago against content hash 17c43800c083, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

analyzing-mach-o-binaries-on-macos 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 11d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/analyst.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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/analyzing-mach-o-binaries-on-macos/SKILL.md · 91 lines

How it starts

The opening of the file, as written. The whole thing — 91 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Analyzing Mach-O Binaries on macOS

When to Use

  • You have a macOS sample (Mach-O) and need a static capability and trust read.
  • You must handle a fat/universal binary containing multiple architecture slices.
  • You need to inspect linked dylibs, entitlements, and code-signing status.

Do not use Windows PE tooling on Mach-O — the formats differ entirely; use Mach-O-aware parsers.

Prerequisites

  • A Mach-O parser (Python stdlib struct, or macholib/LIEF); the sample handled inertly.
  • For signing/entitlements on macOS, codesign/otool are authoritative.

Safety & Handling

  • Parse statically; never execute the sample, especially on a real macOS host.
  • Keep the sample password-protected at rest and reference it by hash.

Workflow

Step 1: Detect fat vs. thin and architecture

Check the magic: 0xCAFEBABE (fat/universal) vs. 0xFEEDFACE/0xFEEDFACF (Mach-O 32/64). For fat binaries, enumerate and analyze each slice.

python scripts/analyst.py header sample.macho

Step 2: Parse load commands

Read load commands for linked dylibs (LC_LOAD_DYLIB), entry point (LC_MAIN), and signing (LC_CODE_SIGNATURE). The dylib list hints at capability (networking, crypto).

Step 3: Inspect entitlements and signing

On macOS, use codesign/otool to read entitlements and verify the signature. Ad-hoc or absent signatures and suspicious entitlements are risk indicators.

Step 4: Infer capability and route

Map linked frameworks/symbols to behaviors and route to disassembly/RE for deeper analysis.

Validation

  • Fat binaries are decomposed and each slice is analyzed, not just the first.
  • Load commands, dylibs, and signing status are enumerated correctly.
  • Capability inferences are corroborated by linked frameworks/symbols.

Pitfalls

  • Analyzing only one slice of a universal binary.
  • Trusting a present signature without verifying it (ad-hoc signatures verify but aren't trusted).
  • Applying PE assumptions (sections/imports) to Mach-O structures.

Read the full file on GitHub · 91 lines

Files

What ships with it

3 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. 11d ago First seen · 91 lines · 75 tokens per session scan A 17c43800c083

Subscribe to this mod's changes

analyzing-mach-o-binaries-on-macos is a skill published in the GitHub repository meltedinhex/analyst-ai-pack (22 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 75 tokens to every session and 780 once invoked, about $0.0004 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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