diffing-malware-samples-to-find-changes

diffing-malware-samples-to-find-changes is a skill for Claude Code, Codex from meltedinhex/analyst-ai-pack. It costs 60 tokens per session (640 once invoked), scanned A, original, Apache-2.0.

A static comparison skill for examining two related malware files and reporting how their structure differs. It compares sections, imported functions, file similarity, and fuzzy hashes when available.

In plain words
What is it for?
It helps track malware variants, identify changed sections and imports, measure similarity, and record findings without executing the samples.
Why use it?
It quickly shows whether two binaries are likely related and where they changed before deeper disassembly work.

Skill for Claude CodeCodex

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

Good fit It helps track malware variants, identify changed sections and imports, measure similarity…

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Install with agentmods
npx agentmods add skills/meltedinhex/analyst-ai-pack/diffing-malware-samples-to-find-changes
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 diffing-malware-samples-to-find-changes
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 diffing-malware-samples-to-find-changes

README.md
[![agentmods](https://agentmods.dev/badge/skills/meltedinhex/analyst-ai-pack/diffing-malware-samples-to-find-changes.svg)](https://agentmods.dev/skills/meltedinhex/analyst-ai-pack/diffing-malware-samples-to-find-changes)
Your own site
<a href="https://agentmods.dev/skills/meltedinhex/analyst-ai-pack/diffing-malware-samples-to-find-changes"><img src="https://agentmods.dev/badge/skills/meltedinhex/analyst-ai-pack/diffing-malware-samples-to-find-changes.svg" alt="Measured on agentmods" height="20"></a>
Per session 60 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 640 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 $0.00060 $0.00640
Opus 5 $0.00030 $0.00320
Sonnet 5 $0.00012 $0.00128
Haiku 4.5 $0.00006 $0.00064

Measured 7d ago against content hash cc843252d582, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

diffing-malware-samples-to-find-changes 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 7d 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/diffing-malware-samples-to-find-changes/SKILL.md · 85 lines

What it actually says

Diffing Malware Samples to Find Changes

When to Use

  • You have two related samples (suspected variants of one family) and want a fast, structural diff before a full BinDiff.
  • You need to quantify similarity and pinpoint changed sections/imports for variant tracking.

Do not use this as authoritative function-level diffing — that requires BinDiff/Diaphora on disassembly. This skill does structural/statistical diffing and executes nothing.

Prerequisites

  • Two sample files (read inertly). Optional: ssdeep/tlsh for fuzzy scores (degrade gracefully).

Workflow

Step 1: Structural diff

python scripts/analyst.py diff a.bin b.bin

Compares file size, per-section SHA-256 and entropy, and the import name sets, reporting added/ removed/changed sections and imports.

Step 2: Similarity score

Reports a byte-level similarity ratio and, if available, ssdeep/tlsh fuzzy-hash comparison scores.

Step 3: Prioritize changed regions

Changed sections (same name, different hash) and new imports are the high-value targets for deeper disassembly diffing.

Step 4: Document

Record what changed and the similarity score to support variant/lineage tracking.

Validation

  • Section comparison keys on section name; identical sections report equal hashes.
  • Import diff lists are accurate (added vs removed vs common).
  • Fuzzy-hash scores are reported only when the library is available, else clearly omitted.

Pitfalls

  • Recompilation shifting addresses makes raw byte diff noisy — rely on section/import structure.
  • Packers making both samples look similar (packed) while the payloads differ — unpack first.
  • Treating a high byte-similarity as proof of same author without corroboration.

References

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. 7d ago First seen · 85 lines · 60 tokens per session scan A cc843252d582

Subscribe to this mod's changes

diffing-malware-samples-to-find-changes is a skill published in the GitHub repository meltedinhex/analyst-ai-pack (22 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 60 tokens to every session and 640 once invoked, about $0.0003 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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