packer-unpacking

packer-unpacking is a skill for Claude Code, Codex from MingyiSecLab/Mingyi-Atlas. It costs 33 tokens per session (1,753 once invoked), scanned A, original, Apache-2.0.

A guide for detecting and unpacking software packers, which compress or obscure compiled programs to make their code harder to inspect. It covers common packers and both automated and manual approaches.

In plain words
What is it for?
Use it to measure entropy, identify packers such as UPX or Themida, apply detection tools, and choose an unpacking strategy.
Why use it?
Packing hides the program's original code from ordinary analysis. Unpacking can expose that code for investigation.

Skill for Claude CodeCodex

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

Good fit Use it to measure entropy, identify packers such as UPX or Themida, apply detection tools, and choose an unpacking strategy.

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Install with agentmods
npx agentmods add skills/mingyiseclab/mingyi-atlas/packer-unpacking
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 MingyiSecLab/Mingyi-Atlas --skill packer-unpacking
Clone the repo
git clone --depth 1 https://github.com/MingyiSecLab/Mingyi-Atlas

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 packer-unpacking

README.md
[![agentmods](https://agentmods.dev/badge/skills/mingyiseclab/mingyi-atlas/packer-unpacking/github.svg)](https://agentmods.dev/skills/mingyiseclab/mingyi-atlas/packer-unpacking)
Your own site
<a href="https://agentmods.dev/skills/mingyiseclab/mingyi-atlas/packer-unpacking"><img src="https://agentmods.dev/badge/skills/mingyiseclab/mingyi-atlas/packer-unpacking/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 packer-unpacking

Your own site · 80×15
<a href="https://agentmods.dev/skills/mingyiseclab/mingyi-atlas/packer-unpacking"><img src="https://agentmods.dev/badge/skills/mingyiseclab/mingyi-atlas/packer-unpacking.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 33 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,753 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 $0.00033 $0.01753
Opus 5 $0.00016 $0.00877
Sonnet 5 $0.00007 $0.00351
Haiku 4.5 $0.00003 $0.00175

Measured 8d ago against content hash d0c441792cd6, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

packer-unpacking 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.

src/skills/standard/reverser/packer-unpacking/SKILL.md · 176 lines

How it starts

The opening of the file, as written. The whole thing — 176 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Packer Unpacking Playbook

Packers compress and/or obfuscate binaries to defeat static analysis. The first job: identify which packer, then dispatch the right unpacker (or manual unpacking strategy if no automated tool exists).

1. Detect packing

# Entropy quick-check (>7.0 across the binary = likely packed)
ent /tmp/sample
# or
python3 -c "
import sys, math
d = open('/tmp/sample','rb').read()
f = [0]*256
for b in d: f[b] += 1
h = -sum((c/len(d))*math.log2(c/len(d)) for c in f if c)
print(f'entropy={h:.3f}')
"

# Section-level entropy via radare2
r2 -qc "iSj" /tmp/sample | jq '.[] | "\(.name): \(.entropy)"'

# Tool-based detection
detect-it-easy /tmp/sample  # most reliable, GUI + CLI
diec /tmp/sample           # CLI for DIE
yara -r /opt/yara-rules/packers/ /tmp/sample

Atlas helper:

bin_packer("/tmp/sample")

2. Common packer signatures

Packer Signature
UPX UPX! magic at section header, sections named UPX0, UPX1
ASPack .aspack section, jump after entry to packed code
Themida .themida section, anti-debug, anti-VM heavy
VMProtect .vmp0, .vmp1 sections; obfuscated EP w/ virtualized handlers
MPRESS .MPRESS1, .MPRESS2 sections
PECompact pec1 section, encrypted sections
Enigma .enigma1, .enigma2 sections
Petite small overlay, .petite section
FSG tiny imports, packed sections
MEW MEW magic in section name
Armadillo runtime decryption, anti-debug (older)

3. Automated unpacking

UPX (easy)

upx -d /tmp/sample -o /tmp/unpacked
file /tmp/unpacked

If upx -d fails with "not packed by UPX", the version field has been tampered with (anti-unpack trick). Fix:

# Patch the version byte back
python3 -c "
d = bytearray(open('/tmp/sample','rb').read())
# Find UPX! magic, fix version
import re
for m in re.finditer(b'UPX!', d):
    d[m.end()] = 0x0d  # set version field
open('/tmp/patched','wb').write(d)
"
upx -d /tmp/patched -o /tmp/unpacked

Read the full file on GitHub · 176 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 · 176 lines · 33 tokens per session scan A d0c441792cd6

Subscribe to this mod's changes

packer-unpacking is a skill published in the GitHub repository MingyiSecLab/Mingyi-Atlas (11 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 33 tokens to every session and 1,753 once invoked, about $0.0002 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 2026-09-03.