building-detection-rules-with-sigma

name	building-detection-rules-with-sigma
description	Builds vendor-agnostic detection rules using the Sigma rule format for threat detection across SIEM platforms including Splunk, Elastic, and Microsoft Sentinel. Use when creating portable detection logic from threat intelligence, mapping rules to MITRE ATT&CK techniques, or converting community Sigma rules into platform-specific queries using sigmac or pySigma backends.
domain	cybersecurity
tags	["soc","sigma","detection-rules","siem","mitre-attack","splunk","elastic","sentinel"]
subdomain	soc-operations
version	1.0
author	oyi77
license	Apache-2.0
d3fend_techniques	["Execution Isolation","Process Termination","Hardware-based Process Isolation","Web Session Access Mediation","Process Suspension"]
nist_csf	["DE.CM-01","DE.AE-02","RS.MA-01","DE.AE-06"]

Building Detection Rules With Sigma

Overview

Cybersecurity skill for building detection rules with sigma. Follows industry best practices and security standards.

When to Use

Trigger phrases:

• "building detection rules with sigma"
• "SOC engineers need to create detection rules portable across multiple SIEM platf"
• "Threat intelligence reports describe TTPs requiring new detection coverage"
• "Existing vendor-specific rules need standardization into a shareable format"

Use this skill when:

• SOC engineers need to create detection rules portable across multiple SIEM platforms
• Threat intelligence reports describe TTPs requiring new detection coverage
• Existing vendor-specific rules need standardization into a shareable format
• The team adopts Sigma as a detection-as-code standard in CI/CD pipelines

Do not use for real-time streaming detection (Sigma is for batch/scheduled searches) or when the target SIEM has native detection features that Sigma cannot express (e.g., Splunk RBA risk scoring).

When NOT to Use

• When you lack proper authorization for testing
• For production systems without change management
• When the task requires legal or compliance expertise beyond technical scope

Prerequisites

• Python 3.8+ with pySigma and appropriate backend (pySigma-backend-splunk, pySigma-backend-elasticsearch, pySigma-backend-microsoft365defender)
• Sigma rule repository cloned: git clone https://github.com/SigmaHQ/sigma.git
• MITRE ATT&CK framework knowledge for technique mapping
• Understanding of target SIEM log source field mappings

Workflow

# Example: IOC detection
import re

IOC_PATTERNS = {
    "ip": r"\b(?:\d{1,3}\.){3}\d{1,3}\b",
    "domain": r"\b[a-z0-9-]+\.[a-z]{2,}\b",
    "hash_md5": r"\b[a-f0-9]{32}\b",
    "hash_sha256": r"\b[a-f0-9]{64}\b",
}

def extract_iocs() -> :
     {k: re.findall(v, text)  k, v  IOC_PATTERNS.items()}