elementalsouls/claude-osint · skills/email-domain-security/SKILL.md

email-domain-security skillA

Name: email-domain-security
Author: elementalsouls

email-domain-security is agent-read markdown (skill) from elementalsouls/claude-osint: Rigorous, defensible email-spoofability verdict and SPF supply-chain risk analysis computed from published DNS alone. Deepens the record-level SPF/DMARC/DKIM/BIMI/MTA-STS/DNSSEC fetch recipes in the offensive-osint arsenal (§16.14) with the reasoning that section doesn't do: a priority-ordered composite verdict for whether an attacker can actually land header-From-spoofed mail in an inbox, and by which vector (exact-domain vs subdomain) — grounded in the single most-misunderstood distinction in .

Indexed from public GitHub and served as immutable, content-addressed versions. Install it pinned to an exact SHA-256 with the mdr CLI, and every file is verified against the hash recorded here before it reaches your agent. The deterministic audit below grades the latest version, and the same file always earns the same grade.

How to install

Latest version

mdr add elementalsouls/claude-osint/email-domain-security@v1

Exact content

mdr add elementalsouls/claude-osint/email-domain-security@sha256:47dfa12c7dff9999

Pin to a label to follow the author's releases, or to a sha256 to freeze the exact bytes forever. Either way the resolved hash is written to mdr.lock, and mdr install reproduces it on any machine.

Badge

[![mdr](https://markdownregistry.com/badge/art_kexj62am5r6gbhng.svg)](https://markdownregistry.com/a/art_kexj62am5r6gbhng)

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Versions

version	committed	commit	size	audit
v1 latest	2026-08-24	f4acf9e	47,075 B	A	view · diff
v1	2026-08-10	66ffd91	47,020 B	A	view · diff
v1	2026-08-06	e0fef8b	47,002 B	A	view

Audit of the latest version

A 17 of 17 checks passed. Deterministic, no model, same answer every run.

pass: Frontmatter block present
pass: Frontmatter declares a name
pass: Frontmatter declares a description
pass: Size between 200 bytes and 200 KB (47075 bytes)
pass: No zero-width or bidi control characters
pass: No instruction hidden inside an HTML comment
pass: No link to an exfiltration or paste host
pass: No credential-shaped string
pass: No instruction to send local credentials anywhere
pass: No text hidden with inline styles
pass: No prompt-injection phrasing
pass: No curl or wget piped into a shell
pass: No recursive delete of root, home or parent
pass: No instruction to read or print local credentials
pass: No base64 blob over 200 characters
pass: No link to a raw IP address
pass: No script tag

Source

GitHub

elementalsouls/claude-osint · 2,543 stars · license MIT · pushed 2026-08-30 · branch main

API

GET https://markdownregistry.com/api/v1/artifacts/art_kexj62am5r6gbhng
GET https://markdownregistry.com/api/v1/resolve?ref=elementalsouls/claude-osint/email-domain-security
GET https://markdownregistry.com/api/v1/blob/47dfa12c7dff999930789222a6efc7bfbcf01a4adc66210892fadb50582e47ba