sigma-rule-writer

sigma-rule-writer is a skill for Claude Code from WRG-11/wrg-sigma-rules. It costs 24 tokens per session (174 once invoked), scanned A, original, MIT.

A guided tool for writing Sigma detection rules, which are shared YAML descriptions of suspicious activity in computer logs. It turns a plain-language threat description into a draft rule after asking about the data source, system, technique, and severity.

In plain words
What is it for?
Use it to draft rules for SIEM or endpoint alerts, describe the logs needed to detect an attack, and connect activity to MITRE ATT&CK techniques.
Why use it?
It helps turn an unclear security concern into detection logic that a security monitoring system can use or adapt.

Skill for Claude Code

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

Part of the wrg-sigma-rules plugin — 3 skills, 1 MCP server shipped together

Good fit Use it to draft rules for SIEM or endpoint alerts, describe the logs needed to detect an attack, and connect activity to MITRE ATT&CK techniques.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/wrg-11/wrg-sigma-rules/sigma-rule-writer
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 WRG-11/wrg-sigma-rules --skill sigma-rule-writer
Clone the repo
git clone --depth 1 https://github.com/WRG-11/wrg-sigma-rules

Made for: Claude Code.

Or install wrg-sigma-rules, the plugin that ships this one along with the rest of its 3 skills, 1 MCP server.

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 sigma-rule-writer

README.md
[![agentmods](https://agentmods.dev/badge/skills/wrg-11/wrg-sigma-rules/sigma-rule-writer/github.svg)](https://agentmods.dev/skills/wrg-11/wrg-sigma-rules/sigma-rule-writer)
Your own site
<a href="https://agentmods.dev/skills/wrg-11/wrg-sigma-rules/sigma-rule-writer"><img src="https://agentmods.dev/badge/skills/wrg-11/wrg-sigma-rules/sigma-rule-writer/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 sigma-rule-writer

Your own site · 80×15
<a href="https://agentmods.dev/skills/wrg-11/wrg-sigma-rules/sigma-rule-writer"><img src="https://agentmods.dev/badge/skills/wrg-11/wrg-sigma-rules/sigma-rule-writer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 24 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 174 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.
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 $0.00024 $0.00174
Opus 5 $0.00012 $0.00087
Sonnet 5 $0.00005 $0.00035
Haiku 4.5 $0.00002 $0.00017

Measured today against content hash 0ed45e122c83, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

sigma-rule-writer 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 today.

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.

plugins/wrg-sigma-rules/skills/sigma-rule-writer/SKILL.md · 18 lines

What it actually says

Sigma Rule Writer

Use the wrg-sigma-rules MCP server's draft_rule tool for a scaffold and immediately call validate_rule on the emitted YAML. Ask only for missing behaviour, telemetry/logsource, target platform, MITRE technique, severity, or source reference.

Do not present a scaffold as deployable. Surface every validator warning, especially placeholder false-positive text, REPLACE_ME markers, missing references, and missing ATT&CK tags. If a SIEM conversion is requested, use convert_rule; for Windows/Sysmon rules pass the sysmon pipeline. Save a rule only when the user names a destination path.

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. today Changed · -132 lines · -94 tokens per session 0ed45e122c83
  2. 11d ago First seen · 150 lines · 118 tokens per session scan A f94836f54a12

Subscribe to this mod's changes

sigma-rule-writer is a skill published in the GitHub repository WRG-11/wrg-sigma-rules (2 stars, last pushed yesterday), licensed MIT. It adds 24 tokens to every session and 174 once invoked, about $0.0001 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 2026-08-31.

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