analyzing-webshells

analyzing-webshells is a skill for Claude Code, Codex from meltedinhex/analyst-ai-pack. It costs 87 tokens per session (741 once invoked), scanned A, original, Apache-2.0.

A static-analysis workflow for examining suspected webshells, which are server-side scripts attackers use as hidden command interfaces.

In plain words
What is it for?
Use it to trace request input to command-execution functions, detect common obfuscation, decode obvious layers, and identify the script’s command interface.
Why use it?
It helps confirm whether a PHP, ASP, ASPX, or JSP file can execute attacker-controlled commands without running it on a live web server.

Skill for Claude CodeCodex

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

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/meltedinhex/analyst-ai-pack/analyzing-webshells
Any agent
npx skills add meltedinhex/analyst-ai-pack --skill analyzing-webshells
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 analyzing-webshells

README.md
[![agentmods](https://agentmods.dev/badge/skills/meltedinhex/analyst-ai-pack/analyzing-webshells.svg)](https://agentmods.dev/skills/meltedinhex/analyst-ai-pack/analyzing-webshells)
Your own site
<a href="https://agentmods.dev/skills/meltedinhex/analyst-ai-pack/analyzing-webshells"><img src="https://agentmods.dev/badge/skills/meltedinhex/analyst-ai-pack/analyzing-webshells.svg" alt="Measured on agentmods" height="20"></a>
Per session 87 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 741 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00087 $0.00741
Opus 5 $0.00044 $0.00370
Sonnet 5 $0.00017 $0.00148
Haiku 4.5 $0.00009 $0.00074

Measured 6d ago against content hash 9549fe275cb4, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

analyzing-webshells 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 6d 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/analyzing-webshells/SKILL.md · 91 lines

How it starts

The opening of the file, as written. The whole thing — 91 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Analyzing Webshells

When to Use

  • You found a suspicious server-side script (.php, .aspx, .jsp, .asp) and need to confirm it is a webshell and understand its command interface.
  • You are triaging a web-server compromise and want to classify dropped scripts.

Do not use a live web server to execute the script to "test" it — that runs attacker code. Analyze the source statically.

Prerequisites

  • The suspect script file(s), read inertly.

Safety & Handling

  • Read the file statically; never deploy or request it on a live server. Defang any URLs.

Workflow

Step 1: Detect execution sinks and input flow

python scripts/analyst.py scan shell.php

Flags dynamic-execution sinks (eval, assert, system, exec, passthru, Runtime.exec, ASPX eval()/Process.Start) and whether request input ($_GET/$_POST/Request) reaches them.

Step 2: Identify obfuscation/encoder chains

Detects base64_decode, gzinflate, str_rot13, eval(chr(...)), hex \x strings, and FromBase64String chains commonly wrapping the payload.

Step 3: Decode obvious layers

Apply base64/rot13/gzinflate where present to reveal the inner command interface (best-effort, non-executing).

Step 4: Classify and report

Note the language, the password/parameter gate (if any), and capabilities (file manager, command exec, SQL, upload); defang IOCs.

Validation

  • A flagged file pairs an execution sink with attacker-controlled input.
  • Encoder chains are identified and, where safe, decoded statically.
  • Capability classification is backed by concrete code evidence.

Pitfalls

  • Legitimate admin tools that also use eval/system — corroborate with input flow.
  • Multi-stage shells that fetch the real logic remotely.
  • Deeply nested or runtime-built obfuscation that static decode only partly unwinds.

References

Read the full file on GitHub · 91 lines

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. 6d ago First seen · 91 lines · 87 tokens per session scan A 9549fe275cb4

Subscribe to this mod's changes

analyzing-webshells is a skill published in the GitHub repository meltedinhex/analyst-ai-pack (22 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 87 tokens to every session and 741 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 2026-08-30.

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