analyzing-email-headers-for-phishing-investigation

analyzing-email-headers-for-phishing-investigation is a skill for Claude Code from Mikaru0Mystic/sectinel. It costs 44 tokens per session (3,033 once invoked), scanned A, a copy of analyzing-email-headers-for-phishing-investigation, Apache-2.0.

A procedure for examining the technical headers attached to an email to trace where it came from and check whether the sender was forged. SPF, DKIM, and DMARC are email checks that help verify sending servers and domains.

In plain words
What is it for?
Use it to parse raw EML or MSG headers, review delivery paths, validate sender checks, investigate clicked phishing links, and assess suspicious IP addresses or domains.
Why use it?
It helps investigators distinguish genuine messages from phishing and spoofed emails, and follow the message's route through mail servers.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the cybersecurity-skills plugin — 56 skills shipped together

Good fit Use it to parse raw EML or MSG headers, review delivery paths, validate sender checks, investigate clicked phishing links, and assess suspicious IP addresses or domains.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/mikaru0mystic/sectinel/analyzing-email-headers-for-phishing-investigation
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 Mikaru0Mystic/sectinel --skill analyzing-email-headers-for-phishing-investigation
Clone the repo
git clone --depth 1 https://github.com/Mikaru0Mystic/sectinel

Made for: Claude Code.

Or install cybersecurity-skills, the plugin that ships this one along with the rest of its 56 skills.

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-email-headers-for-phishing-investigation

README.md
[![agentmods](https://agentmods.dev/badge/skills/mikaru0mystic/sectinel/analyzing-email-headers-for-phishing-investigation/github.svg)](https://agentmods.dev/skills/mikaru0mystic/sectinel/analyzing-email-headers-for-phishing-investigation)
Your own site
<a href="https://agentmods.dev/skills/mikaru0mystic/sectinel/analyzing-email-headers-for-phishing-investigation"><img src="https://agentmods.dev/badge/skills/mikaru0mystic/sectinel/analyzing-email-headers-for-phishing-investigation/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 analyzing-email-headers-for-phishing-investigation

Your own site · 80×15
<a href="https://agentmods.dev/skills/mikaru0mystic/sectinel/analyzing-email-headers-for-phishing-investigation"><img src="https://agentmods.dev/badge/skills/mikaru0mystic/sectinel/analyzing-email-headers-for-phishing-investigation.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 44 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,033 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 94% copy Near-identical to another mod 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 $0.00044 $0.03033
Opus 5 $0.00022 $0.01517
Sonnet 5 $0.00009 $0.00607
Haiku 4.5 $0.00004 $0.00303

Measured 12d ago against content hash b2164607a562, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

analyzing-email-headers-for-phishing-investigation 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 12d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/agent.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.

Makes network callslowCapability

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

curl -s "https://api.abuseipdb.com/api/v2/check?ipAddress=${SENDING_IP}" \
Origin

This is a copy

94% identical to analyzing-email-headers-for-phishing-investigation — 21 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

arsenal/Anthropic-Cybersecurity-Skills/skills/analyzing-email-headers-for-phishing-investigation/SKILL.md · 328 lines

How it starts

The opening of the file, as written. The whole thing — 328 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Analyzing Email Headers for Phishing Investigation

When to Use

  • When investigating a suspected phishing email to determine its true origin
  • For verifying sender authenticity and detecting email spoofing
  • During incident response when a user has clicked a phishing link
  • When tracing the delivery path and relay servers of a suspicious email
  • For validating SPF, DKIM, and DMARC alignment to identify forgery

Prerequisites

  • Raw email headers from the suspicious message (EML or MSG format)
  • Understanding of SMTP protocol and email header fields
  • Access to DNS lookup tools (dig, nslookup) for SPF/DKIM/DMARC verification
  • Email header analysis tools (MHA, emailheaders.net concepts)
  • Python with email parsing libraries for automated analysis
  • Access to threat intelligence platforms for IP/domain reputation

Workflow

Step 1: Extract Raw Email Headers

# Export from Outlook: Open email > File > Properties > Internet Headers
# Export from Gmail: Open email > Three dots > Show original
# Export from Thunderbird: View > Message Source

# If working with EML file from forensic image
cp /mnt/evidence/Users/suspect/AppData/Local/Microsoft/Outlook/phishing_email.eml \
   /cases/case-2024-001/email/

# If working with PST file, extract individual messages
pip install pypff
python3 << 'PYEOF'
import pypff

pst = pypff.file()
pst.open("/cases/case-2024-001/email/outlook.pst")
root = pst.get_root_folder()

def extract_messages(folder, path=""):
    for i in range(folder.get_number_of_sub_messages()):
        msg = folder.get_sub_message(i)
        headers = msg.get_transport_headers()
        subject = msg.get_subject()
        if headers:
            filename = f"/cases/case-2024-001/email/msg_{i}_{subject[:30]}.txt"
            with open(filename, 'w') as f:
                f.write(headers)
    for i in range(folder.get_number_of_sub_folders()):
        extract_messages(folder.get_sub_folder(i))

extract_messages(root)
PYEOF

Step 2: Parse the Email Header Chain

Read the full file on GitHub · 328 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. 12d ago First seen · 328 lines · 44 tokens per session scan A b2164607a562

Subscribe to this mod's changes

analyzing-email-headers-for-phishing-investigation is a skill published in the GitHub repository Mikaru0Mystic/sectinel (11 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 44 tokens to every session and 3,033 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 94% identical to analyzing-email-headers-for-phishing-investigation, differing in 21 lines, and is treated as a copy.

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