code-obfuscation-deobfuscation

A guide for analyzing and undoing code obfuscation, which deliberately makes program code difficult to read or reverse engineer.

In plain words
What is it for?
It supports reverse engineering protected native binaries involving junk code, altered control flow, self-modifying code, virtual machines, or encrypted strings.
Why use it?
It helps distinguish different protection methods and choose an analysis approach for each one.

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/miru-zero/zero-brain/code-obfuscation-deobfuscation
Any agent
npx skills add miru-zero/zero-brain --skill code-obfuscation-deobfuscation
Clone the repo
git clone --depth 1 https://github.com/miru-zero/zero-brain

Made for: Claude Code, Codex.

Per session 51 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,546 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 97% copy Near-identical to another mod 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 $0.00051 $0.03546
Opus 5 $0.00026 $0.01773
Sonnet 5 $0.00010 $0.00709
Haiku 4.5 $0.00005 $0.00355

Measured yesterday against content hash 4368d64f9efd, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

code-obfuscation-deobfuscation 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 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.

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.

Origin

This is a copy

97% identical to code-obfuscation-deobfuscation — 6 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/code-obfuscation-deobfuscation/SKILL.md · 390 lines

How it starts

The opening of the file, as written. The whole thing — 390 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SKILL: Code Obfuscation & Deobfuscation — Expert Analysis Playbook

AI LOAD INSTRUCTION: Expert techniques for identifying, classifying, and defeating code obfuscation in native binaries. Covers junk code, opaque predicates, SMC, control flow flattening, movfuscator, VM protectors (VMProtect/Themida/Code Virtualizer), string encryption, import hiding, and anti-disassembly tricks. Base models often conflate packing with obfuscation and miss the distinction between static and dynamic deobfuscation strategies.

Quick identification picks

Symptom in IDA/Ghidra Likely Obfuscation Start With
Flat CFG, single giant switch Control flow flattening Symbolic execution to recover CFG
Only mov instructions movfuscator demovfuscation / trace-based lifting
pushad/pushfd → VM entry VM protector Handler table extraction
XOR loop before code execution SMC / string encryption Dynamic analysis, breakpoint after decode
Impossible conditions (opaque predicates) Junk code insertion Pattern-based removal
All strings unreadable String encryption Hook decryption routine, or emulate
No imports in IAT Import hiding Trace GetProcAddress / hash resolution

1. JUNK CODE & OPAQUE PREDICATES

1.1 Junk Code Insertion

Dead code that never affects program output, added to increase analysis time.

Identification:

  • Instructions that write to registers/memory never read afterward
  • Function calls whose return values are discarded and have no side effects
  • Loops with invariant bounds that compute unused results

Removal strategy:

  1. Compute def-use chains (IDA/Ghidra data flow analysis)
  2. Mark instructions with no downstream use as dead
  3. Verify removal doesn't change program behavior (trace comparison)

Read the full file on GitHub · 390 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 · 390 lines · 51 tokens per session scan A 4368d64f9efd

Subscribe to this mod's changes

code-obfuscation-deobfuscation is a skill published in the GitHub repository miru-zero/zero-brain (0 stars, last pushed 14d ago), licensed MIT. It adds 51 tokens to every session and 3,546 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 97% identical to code-obfuscation-deobfuscation, differing in 6 lines, and is treated as a copy.

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