What is Linux Malware Analysis?

A workflow for examining Linux ELF files, the executable format used by many Linux programs, to find signs of malware.

Use it to inspect binary metadata, compiler clues, packing, persistence, command-and-control activity, rootkits, cryptominers, and common Go, Rust, or Mirai patterns.

It gives analysts a structured way to identify how a suspicious binary was built, packed, started, kept running, and communicated. It also helps map observed behavior to the MITRE ATT&CK framework, a catalogue of attack techniques.

Linux Malware Analysis — Skill for Claude Code and Codex by buzzer-re

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 buzzer-re/Rikugan --skill linux-malware

Clone the repo

git clone --depth 1 https://github.com/buzzer-re/Rikugan

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/buzzer-re/rikugan/linux-malware/github.svg)](https://agentmods.dev/skills/buzzer-re/rikugan/linux-malware)

Your own site

<a href="https://agentmods.dev/skills/buzzer-re/rikugan/linux-malware"><img src="https://agentmods.dev/badge/skills/buzzer-re/rikugan/linux-malware/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/buzzer-re/rikugan/linux-malware"><img src="https://agentmods.dev/badge/skills/buzzer-re/rikugan/linux-malware.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 4,375 The whole file, excluding the scripts and references it only reads on demand.

Security scan B 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector warn 7 Sept 2026

SkillSpector: 15 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

high Privilege Escalation · line 108
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
high Privilege Escalation · line 126
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
high Privilege Escalation · line 126
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
high Privilege Escalation · line 207
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
high Privilege Escalation · line 127
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
high Privilege Escalation · line 127
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
high Privilege Escalation · line 127
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
high Privilege Escalation · line 128
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
high Privilege Escalation · line 128
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
high YARA Match · line 129
YARA rule matched a known malware signature (reverse shell, backdoor, ransomware, C2 framework, or info stealer).

Fix: Remove the malware payload or compromised file entirely. Investigate how it entered the skill and audit all other artifacts for additional indicators of compromise.
high YARA Match · line 165
YARA rule matched cryptocurrency mining indicators (stratum protocol, mining pools, miner binaries, or cryptojacking scripts).

Fix: Remove all cryptocurrency mining code, pool references, and miner binaries. Mining in agent skills is unauthorized resource abuse. Report the skill as malicious.
high YARA Match · line 165
YARA rule matched cryptocurrency mining indicators (stratum protocol, mining pools, miner binaries, or cryptojacking scripts).

Fix: Remove all cryptocurrency mining code, pool references, and miner binaries. Mining in agent skills is unauthorized resource abuse. Report the skill as malicious.
high YARA Match · line 242
YARA rule matched a known malware signature (reverse shell, backdoor, ransomware, C2 framework, or info stealer).

Fix: Remove the malware payload or compromised file entirely. Investigate how it entered the skill and audit all other artifacts for additional indicators of compromise.
high Privilege Escalation · line 290
Potential security issue detected. Manual review is recommended.

Fix: Review the flagged content for security risks. Ensure no credentials, secrets, or sensitive data are exposed.
medium Rogue Agent · line 246
Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.

Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.

How audits are shown

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.

Model	Per session	Once invoked
Fable 5.1	$0.00043	$0.04375
Opus 5.5	$0.00017	$0.01750
Sonnet 5.5	$0.00009	$0.00875
Haiku 4.5	$0.00004	$0.00438

Measured 1mo ago against content hash 06a308a58fee, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade B, and why

Linux Malware Analysis 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 1mo 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.

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.

~/.bashrc ~/.profile ~/.ssh/authorized_keys

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

rikugan/skills/builtins/linux-malware/SKILL.md · 325 lines

How it starts

The opening of the file, as written. The whole thing — 325 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Task: Linux Malware Analysis. You are a senior malware analyst examining a potentially malicious ELF binary. Defang ALL IOCs in output (hxxps://, [.] notation). Work methodically through each phase. Do not skip phases.

Phase 0: Binary Triage

Run these first — the answers change every subsequent decision.

get_binary_info — ELF class (32/64), architecture, endianness, linkage type, entry point, section count, function count
list_segments — check PT_INTERP (non-standard interpreter path = backdoor dropper), segment permissions (W+X = suspicious), entropy per segment

Determine compiler toolchain:

search_strings for: runtime., go.itab, panicked at → Go binary
search_strings for: core::panicking, _ZN (Rust name mangling), .L__unnamed → Rust binary
Import of pthread_create + libc.so → standard C/C++
search_strings for UPX magic, check function count vs binary size

Packing triage:

Signal	Meaning
`"UPX!"` string present	UPX (may have corrupted header)
<5 functions in a binary >50KB	Packer stub only
Entry point at high address / near end of segment	Self-extracting loader
W+X segment	Runtime code decryption / shellcode loading
No `.symtab`, no section headers	Stripped (normal) but also packing indicator
`search_strings` returns very few results (<10) in large binary	String encryption

UPX header corruption (common in IoT/Mirai variants): The UPX magic 0x55505821 is replaced with random bytes to prevent automated unpacking, but the binary still executes. Note in report, recommend dynamic analysis for full unpacking.

Architecture-specific expectations:

x86_64: Desktop/server malware, containers, cloud; most tools work natively
aarch64 / arm: IoT, embedded, mobile-adjacent; check for ARM debug register checks
mipsel / mipseb: Router/DVR malware (Mirai family); MIPS delay slots complicate disassembly
ppc / ppc64: Rare; router firmware (old Synology, QNAP)

Read the full file on GitHub · 325 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.

1mo ago First seen · 325 lines · 43 tokens per session scan B 06a308a58fee

Subscribe to this mod's changes

Linux Malware Analysis is a skill published in the GitHub repository buzzer-re/Rikugan (690 stars, last pushed 8d ago), licensed MIT. It adds 43 tokens to every session and 4,375 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-08-30.

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