passive-osint

passive-osint is a skill for Claude Code, Codex from FrancescoStabile/numasec. It costs 99 tokens per session (1,603 once invoked), scanned A, original, AGPL-3.0.

A guide to passive OSINT, meaning the collection of publicly available information without sending traffic that could alert the target. It covers domains, email addresses, usernames, subdomains, DNS, and historical web records.

In plain words
What is it for?
Finding subdomains, reviewing certificate records and archived pages, and checking historical DNS or internet-facing information.
Why use it?
It helps map a target’s publicly visible footprint while reducing the chance of triggering alerts.

Skill for Claude CodeCodex

Which agent this was written for is unclear — body not stored (licence); the path alone says nothing.

Good fit Finding subdomains, reviewing certificate records and archived pages, and checking historical DNS or internet-facing information.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/francescostabile/numasec/passive-osint
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 FrancescoStabile/numasec --skill passive-osint
Clone the repo
git clone --depth 1 https://github.com/FrancescoStabile/numasec

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 passive-osint

README.md
[![agentmods](https://agentmods.dev/badge/skills/francescostabile/numasec/passive-osint/github.svg)](https://agentmods.dev/skills/francescostabile/numasec/passive-osint)
Your own site
<a href="https://agentmods.dev/skills/francescostabile/numasec/passive-osint"><img src="https://agentmods.dev/badge/skills/francescostabile/numasec/passive-osint/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.

agentmods 80×15 button for passive-osint

Your own site · 80×15
<a href="https://agentmods.dev/skills/francescostabile/numasec/passive-osint"><img src="https://agentmods.dev/badge/skills/francescostabile/numasec/passive-osint.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 99 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,603 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown 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 $0.00099 $0.01603
Opus 5 $0.00049 $0.00801
Sonnet 5 $0.00020 $0.00321
Haiku 4.5 $0.00010 $0.00160

Measured 10d ago against content hash 4c1f949ef7ef, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

passive-osint scanned grade A 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 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.

Makes network callslowCapability

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

curl -s "https://crt.sh/?q=%25.example.com&output=json" | jq -r '.[].name_value' | sort -u
packages/numasec/skills/passive-osint/SKILL.md · 134 lines

The source is not reproduced here

Licensed AGPL-3.0

The repository is licensed AGPL-3.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

Read it on GitHub

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. 10d ago First seen · 134 lines · 99 tokens per session scan A 4c1f949ef7ef

Subscribe to this mod's changes

passive-osint is a skill published in the GitHub repository FrancescoStabile/numasec (768 stars, last pushed 4mo ago), licensed AGPL-3.0. It adds 99 tokens to every session and 1,603 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 1 finding (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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