reverse-engineering-nim-and-other-exotic-binaries

reverse-engineering-nim-and-other-exotic-binaries is a skill for Claude Code, Codex from meltedinhex/analyst-ai-pack. It costs 80 tokens per session (722 once invoked), scanned A, original, Apache-2.0.

A guide to analysing malware compiled with less common languages such as Nim, Crystal, V, Zig, or D by recognising their runtime code and naming patterns.

In plain words
What is it for?
Use it to identify the source language, find startup and error-handling code, recognise runtime strings, and recover readable names from mangled symbols.
Why use it?
Compiler-generated code can look unfamiliar and make it difficult to find the program's main logic. Language-specific clues provide landmarks for navigating the binary.

Skill for Claude CodeCodex

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

Good fit Use it to identify the source language, find startup and error-handling code, recognise runtime strings, and recover readable names from mangled symbols.

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Install with agentmods
npx agentmods add skills/meltedinhex/analyst-ai-pack/reverse-engineering-nim-and-other-exotic-binaries
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 reverse-engineering-nim-and-other-exotic-binaries
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 reverse-engineering-nim-and-other-exotic-binaries

README.md
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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.

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<a href="https://agentmods.dev/skills/meltedinhex/analyst-ai-pack/reverse-engineering-nim-and-other-exotic-binaries"><img src="https://agentmods.dev/badge/skills/meltedinhex/analyst-ai-pack/reverse-engineering-nim-and-other-exotic-binaries.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 80 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 722 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 $0.00080 $0.00722
Opus 5 $0.00040 $0.00361
Sonnet 5 $0.00016 $0.00144
Haiku 4.5 $0.00008 $0.00072

Measured 9d ago against content hash f0d99a55db56, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

reverse-engineering-nim-and-other-exotic-binaries 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 9d 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/reverse-engineering-nim-and-other-exotic-binaries/SKILL.md · 91 lines

What it actually says

Reverse Engineering Nim and Other Exotic Binaries

When to Use

  • You have a compiled binary that is not C/C++/Go/Rust/.NET and need to identify its source language (Nim, Crystal, V, Zig, D) to orient analysis.
  • Symbol/runtime patterns are unfamiliar and you want language-specific landmarks.

Do not use this for already-supported languages (Go/Rust have dedicated skills). This skill reads the binary statically and executes nothing.

Prerequisites

  • The binary (read inertly).

Safety & Handling

  • Read bytes statically; treat strings as untrusted.

Workflow

Step 1: Detect the source language

python scripts/analyst.py detect sample.bin

Scans for language runtime signatures: Nim (@m..nim, nimrtl, fatal.nim, stack trace, @ /nim), Crystal (Crystal::, crystal-lang), V (vlib/, _vinit), Zig (zig, panic: , std.builtin), and D (_Dmain, core.runtime, TypeInfo_).

Step 2: Locate runtime landmarks

Use the detected language's panic/exception and module strings to find main/init and error paths.

Step 3: Handle name mangling

Apply the language's mangling convention (e.g., Nim's proc__module_NNN) to recover readable names.

Step 4: Proceed with analysis

With the language identified, analyze logic; many exotic-language samples wrap the same C2/loader behavior.

Validation

  • Language detection is based on multiple corroborating runtime strings, not one weak hit.
  • Identified landmarks (panic/init) are consistent with the language.
  • Name demangling matches the language's documented scheme.

Pitfalls

  • Statically linked C runtime strings causing misclassification — weight language-specific markers.
  • Stripped binaries with few runtime strings.
  • Stagers in exotic languages that quickly hand off to shellcode.

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. 9d ago First seen · 91 lines · 80 tokens per session scan A f0d99a55db56

Subscribe to this mod's changes

reverse-engineering-nim-and-other-exotic-binaries is a skill published in the GitHub repository meltedinhex/analyst-ai-pack (22 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 80 tokens to every session and 722 once invoked, about $0.0004 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.

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