dotnet-reversing

dotnet-reversing is a skill for Claude Code, Codex from ogrodev/fsociety. It costs 442 tokens per session (2,910 once invoked), scanned A, original, MIT.

A toolkit and method for examining programs built with .NET, Microsoft's software platform, including C# and Visual Basic programs. It explains how to identify, inspect, and decompile .NET program files into more readable code.

In plain words
What is it for?
Use it to inspect .NET executables and libraries, understand their structure and behavior, and investigate obfuscated or protected programs.
Why use it?
It helps when the original source code is unavailable and ordinary native-program analysis tools are not suitable.

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/ogrodev/fsociety/dotnet-reversing
Any agent
npx skills add ogrodev/fsociety --skill dotnet-reversing
Clone the repo
git clone --depth 1 https://github.com/ogrodev/fsociety

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 dotnet-reversing

README.md
[![agentmods](https://agentmods.dev/badge/skills/ogrodev/fsociety/dotnet-reversing.svg)](https://agentmods.dev/skills/ogrodev/fsociety/dotnet-reversing)
Your own site
<a href="https://agentmods.dev/skills/ogrodev/fsociety/dotnet-reversing"><img src="https://agentmods.dev/badge/skills/ogrodev/fsociety/dotnet-reversing.svg" alt="Measured on agentmods" height="20"></a>
Per session 442 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,910 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 $0.00442 $0.02910
Opus 5 $0.00221 $0.01455
Sonnet 5 $0.00088 $0.00582
Haiku 4.5 $0.00044 $0.00291

Measured 4d ago against content hash e249bf4bee97, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

dotnet-reversing 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 4d 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.

romero/skills/dotnet-reversing/SKILL.md · 294 lines

How it starts

The opening of the file, as written. The whole thing — 294 lines — stays where its author put it; the contents beside it link to each section on GitHub.

.NET Reverse Engineering

Why .NET Is Different

.NET binaries ship IL (Intermediate Language) code with full metadata — type names, method signatures, string literals, inheritance hierarchies. This makes decompilation far more effective than with native code. A clean .NET binary decompiles to near-source-quality C#. Obfuscation raises the bar but never eliminates the metadata entirely because the CLR needs it to execute.

This matters for offensive work: .NET malware leaks intent through its metadata. Even heavily obfuscated samples expose type references to System.Net.Sockets, System.Security.Cryptography, or System.Runtime.InteropServices — revealing capability before you touch the IL.

Detection — Is This .NET?

Confirm a binary is .NET before choosing your toolchain. Wrong tools waste time.

# Quick check — file magic
file <binary>
# Look for: "Mono/.Net assembly" or "PE32 executable ... Mono/.Net"

# Confirm via PE imports — .NET binaries import mscoree.dll
r2 -qc 'ii~mscoree' <binary>
# _CorExeMain = .NET EXE, _CorDllMain = .NET DLL

# CLI header presence — Data Directory entry 14
r2 -qc 'iH~CLR' <binary>

# monodis sanity check
monodis --assembly <binary>

If the binary is mixed-mode (C++/CLI), it has both native and managed code. Use monodis for the managed portion and radare2/Ghidra for native.

Core Workflow

Follow this sequence for any .NET target. Skip steps that do not apply, but never skip triage.

Phase 1 — Triage and Metadata Extraction

Goal: understand what you have before deep analysis.

# Assembly identity
monodis --assembly <binary>

# Type inventory — namespaces reveal purpose
monodis --typedef <binary>

# External dependencies — what frameworks/libraries does it use?
monodis --assemblyref <binary>
monodis --typeref <binary>

# Entry point identification
monodis --method <binary> | grep -A5 "\.entrypoint"

# Embedded resources — configs, encrypted payloads, embedded DLLs
monodis --manifest <binary>

# String extraction — URLs, IPs, registry keys, crypto constants
strings -el <binary>   # Unicode strings (common in .NET)
strings -a <binary>    # ASCII strings
floss <binary>         # FLARE obfuscated string solver

Read the full file on GitHub · 294 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. 4d ago First seen · 294 lines · 442 tokens per session scan A e249bf4bee97

Subscribe to this mod's changes

dotnet-reversing is a skill published in the GitHub repository ogrodev/fsociety (20 stars, last pushed 5mo ago), licensed MIT. It adds 442 tokens to every session and 2,910 once invoked, about $0.0022 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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