security-investigator: Skill for Claude Code

.github/skills/incident-investigation/SKILL.md

incident-investigation is a skill for Claude Code, Codex from SCStelz/security-investigator. It costs 97 tokens per session (8,575 once invoked), scanned A, original, MIT.

A guide for investigating security incidents in Microsoft Defender XDR and Microsoft Sentinel, Microsoft's platforms for detecting and investigating threats. It starts with an incident's alerts, affected assets, and evidence, then examines selected entities.

In plain words
What is it for?
Use it to investigate an incident ID, review alerts and affected devices or accounts, and examine indicators such as IP addresses, URLs, domains, and file hashes.
Why use it?
It organizes incident triage so analysts can move from the incident overview to focused investigations without manually gathering every related detail.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

This is SCStelz/security-investigator's own configuration. It tells Claude Code and Codex how to work on security-investigator itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything security-investigator configures →

Reuse

Borrowing it

Nothing to install: this file belongs to SCStelz/security-investigator. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/SCStelz/security-investigator/main/.github/skills/incident-investigation/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/SCStelz/security-investigator

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 incident-investigation

README.md
[![agentmods](https://agentmods.dev/badge/skills/scstelz/security-investigator/incident-investigation/github.svg)](https://agentmods.dev/skills/scstelz/security-investigator/incident-investigation)
Your own site
<a href="https://agentmods.dev/skills/scstelz/security-investigator/incident-investigation"><img src="https://agentmods.dev/badge/skills/scstelz/security-investigator/incident-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 incident-investigation

Your own site · 80×15
<a href="https://agentmods.dev/skills/scstelz/security-investigator/incident-investigation"><img src="https://agentmods.dev/badge/skills/scstelz/security-investigator/incident-investigation.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 97 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 8,575 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 12 findings, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Agent Snooping · line 51
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 336
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 531
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 891
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 52
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 369
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 535
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 892
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 53
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 400
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 539
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 893
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
How audits are shown
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 5.1 $0.00097 $0.08575
Opus 5 $0.00048 $0.04287
Sonnet 5 $0.00019 $0.01715
Haiku 4.5 $0.00010 $0.00857

Measured 13d ago against content hash c23a0db8f558, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

incident-investigation 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 13d 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.

.github/skills/incident-investigation/SKILL.md · 896 lines

How it starts

The opening of the file, as written. The whole thing — 896 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Incident Investigation - Instructions

Purpose

This skill performs comprehensive security investigations on incidents from Microsoft Defender XDR and Microsoft Sentinel. It retrieves incident details, lists alerts, enumerates assets and evidences, and then performs deep investigation on user-selected entities using appropriate tools and specialized skills.

Investigation Flow:

  1. Phase 1: Incident Description - Retrieve metadata, alerts, assets, and evidences
  2. Phase 2: Incident Investigation Menu - Ask the user to select the incident assets and entities that should be investigated.
  3. Phase 2-A: User Investigation - Follow user-investigation skill workflow
  4. Phase 2-B: Device Investigation - Follow computer-investigation skill workflow
  5. Phase 2-C: IoC Investigation - Follow ioc-investigation skill workflow for IPs, URLs, Files, Domains, Hashes
  6. Phase 3: Looping to Phase 2 - Ask the user to select the further assets and entities that should be investigated.

📑 TABLE OF CONTENTS

  1. Critical Workflow Rules - Start here!
  2. Phase 1: Incident Description - Metadata, Alerts, Assets, Evidences
  3. Phase 2: Incident Investigation Menu - Presenting the options
  4. Phase 2-A: User Investigation - Using user-investigation skill
  5. Phase 2-B: Device Investigation - Using computer-investigation skill
  6. Phase 2-C: IoC Investigation - Using ioc-investigation skill (IPs, URLs, Files, Domains, Hashes)
  7. Phase 3: Post Incident Investigation - Looping to phase 2
  8. JSON Export Structure - Required fields
  9. Error Handling - Troubleshooting guide

⚠️ CRITICAL WORKFLOW RULES - READ FIRST ⚠️

Before starting ANY incident investigation:

Read the full file on GitHub · 896 lines

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. 13d ago First seen · 896 lines · 97 tokens per session scan A c23a0db8f558

Subscribe to this mod's changes

incident-investigation is a skill published in the GitHub repository SCStelz/security-investigator (245 stars, last pushed 4d ago), licensed MIT. It adds 97 tokens to every session and 8,575 once invoked, about $0.0005 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 2026-08-30.

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