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.
npx skills add EvilFreelancer/secs --skill hunting-web-backdoorsgit clone --depth 1 https://github.com/EvilFreelancer/secsWrote 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.
[](https://agentmods.dev/skills/evilfreelancer/secs/hunting-web-backdoors)<a href="https://agentmods.dev/skills/evilfreelancer/secs/hunting-web-backdoors"><img src="https://agentmods.dev/badge/skills/evilfreelancer/secs/hunting-web-backdoors/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.
<a href="https://agentmods.dev/skills/evilfreelancer/secs/hunting-web-backdoors"><img src="https://agentmods.dev/badge/skills/evilfreelancer/secs/hunting-web-backdoors.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00117 | $0.01649 |
| Opus 5 | $0.00059 | $0.00825 |
| Sonnet 5 | $0.00023 | $0.00330 |
| Haiku 4.5 | $0.00012 | $0.00165 |
Grade A, and why
hunting-web-backdoors 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 10d 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.
How it starts
The opening of the file, as written. The whole thing — 115 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Hunting Web Backdoors
A webshell is a legitimate-looking file in a place that serves code, dropped
after an attacker got write access, that turns an HTTP request into command
execution. It is among the most durable footholds on internet-facing systems and
among the easiest to overlook, because it is a valid .php/.aspx/.jsp file
sitting in a directory full of valid files. You cannot find it by asking "is this
malware" one file at a time; you find it by three orthogonal lenses — what
changed, what the content can do, and how the file behaves when requested —
and by trusting the overlap.
Confirm the host is in scope per AGENTS.md. Preserve before you poke: on a live suspect server, capture the web root and logs (and memory, if warranted) before touching files, so timestamps and the shell itself are not contaminated by your own activity.
When to Use
- A web server is suspected of harboring a planted shell or backdoor
- Sweeping web roots after a confirmed or suspected exploitation
- Confirming or refuting a hunt lead or alert pointing at web infrastructure
- Establishing whether a known web vulnerability was actually used to plant a shell
When NOT to Use
- Testing for the upload/RCE flaw itself — use
testing-web-applications; this skill hunts the result, that one finds the hole - Deep analysis of a shell you already found — hand the sample to
analyzing-malware - Generic hypothesis-driven hunting across all telemetry — use
hunting-threats; this is the web-root-specific procedure - On-host artifacts beyond the web root (registry, services) — use
investigating-windows-endpoints, orresponding-to-incidentsfor a Linux host - Confirmed active intrusion — switch to
responding-to-incidents
Three Lenses (trust the overlap)
1. Change — what appeared or was modified in the web root. New or recently
modified files in served directories, especially upload/, images/, tmp/,
and cache paths that should never contain executable content:
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.
- 10d ago First seen · 115 lines · 117 tokens per session scan A cca688f2b185
hunting-web-backdoors is a skill published in the GitHub repository EvilFreelancer/secs (10 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 117 tokens to every session and 1,649 once invoked, about $0.0006 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 2026-08-31.
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