reverse-engineering

A guide to examining compiled programs, firmware, malware, and undocumented communication formats without their original source code.

In plain words
What is it for?
Identifying binary files, extracting strings and symbols, disassembling and decompiling programs, analyzing firmware and protocols, and solving authorized security challenges.
Why use it?
It gives a structured way to understand how software works, find weaknesses, investigate malware, or compare changed binary code.

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/jessefmoore/offensive-claude-code/reverse-engineering
Any agent
npx skills add jessefmoore/offensive-claude-code --skill reverse-engineering
Clone the repo
git clone --depth 1 https://github.com/jessefmoore/offensive-claude-code

Made for: Claude Code, Codex.

Per session 30 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,461 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 1 finding. 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 $0.00030 $0.01461
Opus 5 $0.00015 $0.00731
Sonnet 5 $0.00006 $0.00292
Haiku 4.5 $0.00003 $0.00146

Measured yesterday against content hash 3af38589ef9c, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

reverse-engineering scanned grade B with 1 finding 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.

Reaches for credential filesmediumPrivilege escalation

SSH keys, cloud credentials, git-credentials, .npmrc, /etc/shadow: reading these is how a config file becomes a credential leak.

# - /etc/shadow, /etc/passwd (hardcoded creds)

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

skills/reverse-engineering/SKILL.md · 206 lines

How it starts

The opening of the file, as written. The whole thing — 206 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Reverse Engineering

When to Activate

  • Analyzing compiled binaries for vulnerabilities
  • Understanding proprietary protocols or file formats
  • Malware analysis and unpacking
  • Firmware extraction and analysis
  • Bypassing anti-debugging/anti-tampering protections
  • CTF binary challenges
  • Patch diffing to find 1-day vulnerabilities

Static Analysis

Initial Triage

# File identification
file target_binary
rabin2 -I target_binary  # binary info (arch, bits, endian, protections)

# Strings extraction
strings -n 8 target_binary | grep -iE '(password|key|secret|flag|http|/bin)'
rabin2 -z target_binary   # strings with addresses
rabin2 -zz target_binary  # all strings including wide

# Imports/Exports
rabin2 -i target_binary   # imports
rabin2 -E target_binary   # exports
objdump -T target_binary  # dynamic symbols

# Security mitigations
checksec --file=target_binary
# RELRO, Stack Canary, NX, PIE, FORTIFY

Disassembly & Decompilation

# Ghidra headless analysis
analyzeHeadless /tmp/ghidra_project proj -import target_binary \
  -postScript ExportDecompilation.java -scriptPath /scripts/

# radare2 analysis
r2 -A target_binary
> afl          # list functions
> axt @sym.target_func  # xrefs to function
> pdf @main    # disassemble function
> VV @main     # visual graph mode
> afn new_name @addr  # rename function

# IDA (via MCP or IDAPython)
# Decompile function, rename variables, set types
# Cross-references: xrefs_to(addr), xrefs_from(addr)

Pattern Recognition

# Common vulnerability patterns in disassembly:
# - strcpy/sprintf without bounds → buffer overflow
# - malloc(user_controlled_size) → integer overflow
# - free() followed by use → UAF
# - system()/exec() with user data → command injection
# - Custom crypto (XOR loops, fixed keys) → weak encryption

Dynamic Analysis

Debugging

# GDB with pwndbg/GEF
gdb -q ./target
> break *main
> run
> vmmap              # memory layout
> heap              # heap state
> telescope $rsp 20 # stack inspection
> search-pattern "AAAA"  # find pattern in memory

# Conditional breakpoints
> break *0x401234 if $rax == 0x41414141
> commands
>   x/s $rdi
>   continue
> end

# Anti-debug bypass
> catch syscall ptrace
> commands
>   set $rax = 0
>   continue
> end

Read the full file on GitHub · 206 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 · 206 lines · 30 tokens per session scan B 3af38589ef9c

Subscribe to this mod's changes

reverse-engineering is a skill published in the GitHub repository jessefmoore/offensive-claude-code (2 stars, last pushed 3mo ago), licensed MIT. It adds 30 tokens to every session and 1,461 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it B with 1 finding (reaches for credential files). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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