slv-firewall

slv-firewall is a skill for Claude Code, Codex from ValidatorsDAO/slv. It costs 0 tokens per session (2,234 once invoked), scanned D, original, Apache-2.0.

A guided setup for securing a server's network perimeter with nftables, a Linux firewall, fail2ban, which blocks repeated login attacks, and SSH keys instead of passwords.

In plain words
What is it for?
Use it to set a default-block firewall, protect SSH from repeated attacks, turn off SSH password login, and allow only selected network access.
Why use it?
It reduces exposure to unwanted network access and brute-force SSH attempts without requiring manual file editing.

Skill for Claude CodeCodex

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/validatorsdao/slv/slv-firewall
Any agent
npx skills add ValidatorsDAO/slv --skill slv-firewall
Clone the repo
git clone --depth 1 https://github.com/ValidatorsDAO/slv

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 slv-firewall

README.md
[![agentmods](https://agentmods.dev/badge/skills/validatorsdao/slv/slv-firewall.svg)](https://agentmods.dev/skills/validatorsdao/slv/slv-firewall)
Your own site
<a href="https://agentmods.dev/skills/validatorsdao/slv/slv-firewall"><img src="https://agentmods.dev/badge/skills/validatorsdao/slv/slv-firewall.svg" alt="Measured on agentmods" height="20"></a>
Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,234 The whole file, excluding the scripts and references it only reads on demand.
Security scan D 3 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 $0.00000 $0.02234
Opus 5 $0.00000 $0.01117
Sonnet 5 $0.00000 $0.00447
Haiku 4.5 $0.00000 $0.00223

Measured 3d ago against content hash 084d14df4e7a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade D, and why

slv-firewall scanned grade D with 3 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 3d 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.

Asks for rootmediumPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

- `run_command: sudo nft list ruleset 2>/dev/null | head -3` — is nftables already configured?

Reaches for credential fileshighPrivilege escalation

SSH keys, cloud credentials, git-credentials, .npmrc, /etc/shadow: reading these is how a config file becomes a credential leak.

> "Paste your SSH public key. It's a one-line string starting with `ssh-ed25519` or `ssh-rsa` — usually in `~/.ssh/id_ed25519.pub` on your laptop.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- `run_command: curl -s https://api.ipify.org` — THIS host's public IP (so you filter it out of whitelist candidates — no point whitelisting the server to itself).
oss-skills/slv-firewall/SKILL.md · 223 lines

How it starts

The opening of the file, as written. The whole thing — 223 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SLV Firewall Skill

Lock down the SLV host's network perimeter: nftables default-drop, fail2ban for brute-force, SSH key-based login with password auth off. Non-engineer friendly — three commands, zero file editing.

Related: For phone/laptop VPN on top of this, see the slv-wireguard skill. For automatic HTTPS on the chat UI, see slv install nginx.

Use this skill when the user says anything like:

  • "help me lock down the firewall / SSH"
  • "is my box exposed? / what ports are open?"
  • "allow only my IP" / "whitelist my laptop"
  • "turn off SSH passwords" / "disable password login"
  • "nftables" / "fail2ban" / "brute force"

EL's walkthrough (run in this order — skipping ahead locks users out)

Step 0 — Sanity probe (read-only, parallelizable)

Fire these in parallel so the rest of the conversation has real data to work with:

  • get_premium_vps_my_vps (MCP) — user's Premium VPS list.
  • get_super_vps_my_vps (MCP) — Super VPS list.
  • get_baremetal_status (MCP) — BareMetal list.
  • run_command: curl -s https://api.ipify.org — THIS host's public IP (so you filter it out of whitelist candidates — no point whitelisting the server to itself).
  • run_command: sudo nft list ruleset 2>/dev/null | head -3 — is nftables already configured?
  • run_command: systemctl is-active fail2ban 2>/dev/null — is fail2ban running?
  • run_command: sudo grep -r PasswordAuthentication /etc/ssh/ — is password auth still on?

Use the results to:

  • Say what's already on / off.
  • Build the whitelist candidate list: every ip from the MCP VPS/BM calls that isn't THIS host's IP. Present to the user verbatim:

    "Your SLV account has these other hosts — want them whitelisted? You'll still be able to SSH between them after we lock down."

Step 1 — How will the user reach this box from outside?

Before collecting any --allow IPs, decide the remote-access method with the user. This single question prevents the #1 support ticket (self-lockout from a rotating home IP).

Read the full file on GitHub · 223 lines

Files

What ships with it

1 file 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. 3d ago First seen · 223 lines · 0 tokens per session scan D 084d14df4e7a

Subscribe to this mod's changes

slv-firewall is a skill published in the GitHub repository ValidatorsDAO/slv (89 stars, last pushed 12d ago), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 2,234 tokens. A static security scan graded it D with 3 findings (asks for root, reaches for credential files, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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