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detection-sigma Generic detection rule creation and management using Sigma, the universal SIEM rule format. Sigma provides vendor-agnostic detection logic for log analysis across multiple SIEM platforms. Use when: (1) Creating detection rules for security monitoring, (2) Converting rules between SIEM platforms (Splunk, Elastic, QRadar, Sentinel), (3) Threat hunting with standardized detection patterns, (4) Building detection-as-code pipelines, (5) Mapping detections to MITRE ATT&CK tactics, (6) Implementing compliance-based monitoring rules.
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name detection-sigma description Generic detection rule creation and management using Sigma, the universal SIEM rule format. Sigma provides vendor-agnostic detection logic for log analysis across multiple SIEM platforms. Use when: (1) Creating detection rules for security monitoring, (2) Converting rules between SIEM platforms (Splunk, Elastic, QRadar, Sentinel), (3) Threat hunting with standardized detection patterns, (4) Building detection-as-code pipelines, (5) Mapping detections to MITRE ATT&CK tactics, (6) Implementing compliance-based monitoring rules.
version 0.1.0 maintainer SirAppSec category incident-response tags ["sigma","detection","siem","threat-hunting","mitre-attack","detection-engineering","log-analysis"] frameworks ["MITRE-ATT&CK","NIST","ISO27001"] dependencies {"python":">=3.8","packages":["pysigma","pysigma-backend-splunk","pysigma-backend-elasticsearch","pyyaml"]} references ["https://github.com/SigmaHQ/sigma","https://github.com/SigmaHQ/pySigma","https://sigmahq.io/"]
Sigma Detection Engineering
Overview
Sigma is to log detection what Snort is to network traffic and YARA is to files - a universal signature format for describing security-relevant log events. This skill helps create, validate, and convert Sigma rules for deployment across multiple SIEM platforms, enabling detection-as-code workflows.
Core capabilities :
Create detection rules using Sigma format
Convert rules to 25+ SIEM/EDR backends (Splunk, Elastic, QRadar, Sentinel, etc.)
Validate rule syntax and logic
Map detections to MITRE ATT&CK framework
Build threat hunting queries
Implement compliance-based monitoring
Quick Start
Install Dependencies
pip install pysigma pysigma-backend-splunk pysigma-backend-elasticsearch pyyaml
Create a Basic Sigma Rule
title: Suspicious PowerShell Execution
id: 7d6d30b8-5b91-4b90-a71e-4f5a3f5a3c3f
status: experimental
description: Detects suspicious PowerShell execution with encoded commands
references:
- https://attack.mitre.org/techniques/T1059/001/
author: Your Name
date: YYYY/MM/DD
modified: YYYY/MM/DD
tags:
- attack.execution
- attack.t1059.001
logsource:
category: process_creation
product: windows
detection:
selection:
Image|endswith:
'\powershell.exe'
CommandLine|contains:
-
'-enc'
-
'-EncodedCommand'
-
'FromBase64String'
condition:
selection
falsepositives:
-
Legitimate
administrative
scripts
level:
medium
Convert Rule to Target SIEM
python scripts/sigma_convert.py rule.yml --backend splunk
python scripts/sigma_convert.py rule.yml --backend elasticsearch
python scripts/sigma_convert.py rule.yml --backend sentinel
Core Workflows
Workflow 1: Detection Rule Development Progress:
[ ] 1. Identify detection requirement from threat intelligence or compliance
[ ] 2. Research log sources and field mappings for target environment
[ ] 3. Create Sigma rule using standard template
[ ] 4. Validate rule syntax: python scripts/sigma_validate.py rule.yml
[ ] 5. Test rule against sample logs or historical data
[ ] 6. Convert to target SIEM format
[ ] 7. Deploy and tune based on false positive rate
[ ] 8. Document rule metadata and MITRE ATT&CK mapping
Work through each step systematically. Check off completed items.
Workflow 2: Threat Hunting Rule Creation For proactive threat hunting based on TTPs:
Select MITRE ATT&CK Technique
Identify Log Sources
Determine which logs capture the technique
Map log source categories (process_creation, network_connection, file_event)
Verify log source availability in your environment
Define Detection Logic
Create selection criteria matching suspicious patterns
Add filters to reduce false positives
Use field modifiers for robust matching (endswith, contains, re)
Validate and Test
Run validation: python scripts/sigma_validate.py hunting-rule.yml
Test against known-good and known-bad samples
Tune detection logic based on results
Document and Deploy
Add references to threat reports
Document false positive scenarios
Convert and deploy to production SIEM
Workflow 3: Bulk Rule Conversion When migrating between SIEM platforms:
python scripts/sigma_validate.py --directory rules/ --report validation-report.json
python scripts/sigma_convert.py --directory rules/ --backend splunk --output converted/
python scripts/sigma_convert.py --directory rules/ --backend splunk --report conversion-report.md
Review conversion report for:
Successfully converted rules
Rules requiring manual adjustment
Unsupported field mappings
Backend-specific limitations
Workflow 4: Compliance-Based Detection For implementing compliance monitoring (PCI-DSS, NIST, ISO 27001):
Map Requirements to Detections
Create Detection Rules
Use compliance rule templates from assets/compliance-rules/
Tag rules with compliance framework (e.g., tags: [pci-dss.10.2.5])
Set appropriate severity levels
Validate Coverage
Run: python scripts/compliance_coverage.py --framework pci-dss
Review coverage gaps
Create additional rules as needed
Generate Compliance Report
Document detection coverage by control
Include sample queries and expected alerts
Maintain audit trail for compliance evidence
Rule Structure Reference
Required Fields title: Human-readable rule name
id: UUID (generate with: python -c "import uuid; print(uuid.uuid4())" )
status: stable|test|experimental|deprecated
description: Detailed description of what this detects
author: Your Name
date: YYYY/MM/DD
modified: YYYY/MM/DD
logsource:
category: process_creation|network_connection|file_event|...
product: windows|linux|macos|azure|aws|...
detection:
selection:
FieldName: value
condition: selection
level: informational|low|medium|high|critical
Optional Fields references:
- https://attack.mitre.org/techniques/T1059/
tags:
- attack.execution
- attack.t1059.001
falsepositives:
- Legitimate use cases
fields:
- CommandLine
- User
- ParentImage
Detection Conditions
detection:
selection:
Field: value
condition: selection
detection:
selection:
Field1: value1
Field2: value2
condition: selection
detection:
selection1:
Field: value1
selection2:
Field: value2
condition: selection1 or selection2
detection:
selection:
Field: suspicious_value
filter:
Field: legitimate_value
condition: selection and not filter
detection:
selection:
EventID: 4688
suspicious_cmd:
CommandLine|contains:
- 'powershell'
- 'cmd.exe'
filter_legitimate:
ParentImage|endswith: '\explorer.exe'
condition: selection and suspicious_cmd and not filter_legitimate
Field Modifiers Common modifiers for flexible matching:
|contains - Contains substring (case-insensitive)|endswith - Ends with string|startswith - Starts with string|re - Regular expression match|all - All values must match|base64 - Base64-encoded value matching|base64offset - Base64 with offset variations detection:
selection:
CommandLine|contains|all:
- 'powershell'
- '-enc'
Image|endswith: '\powershell.exe'
Security Considerations
Sensitive Data Handling : Sigma rules may reference sensitive field names or patterns. Store rules in version control with appropriate access controls. Avoid including actual sensitive data in example values.
Access Control : Detection rules reveal defensive capabilities to adversaries. Implement role-based access for rule repositories. Limit rule modification to authorized detection engineers.
Audit Logging : Log all rule deployments, modifications, and deletions. Track who deployed which rules to which systems. Maintain change history for compliance auditing.
Compliance : Sigma rules support compliance monitoring (PCI-DSS 10.2, NIST SP 800-53 AU family, ISO 27001 A.12.4). Document rule-to-control mappings for audit evidence.
Safe Defaults : Use conservative false positive filtering in production. Start rules at "experimental" status. Test thoroughly in test environment before production deployment.
Bundled Resources
Scripts
scripts/sigma_convert.py - Convert Sigma rules to target SIEM backend formatsscripts/sigma_validate.py - Validate Sigma rule syntax and detect common errorsscripts/compliance_coverage.py - Analyze detection coverage for compliance frameworksscripts/generate_rule_template.py - Generate Sigma rule template with MITRE ATT&CK tags
References
references/mitre-attack-mapping.md - Common MITRE ATT&CK techniques and Sigma detection patternsreferences/log-source-guide.md - Log source categories, products, and field mappingsreferences/compliance-mappings.md - Compliance framework to detection rule mappingsreferences/backend-support.md - Supported SIEM backends and conversion capabilitiesreferences/field-modifiers.md - Comprehensive guide to Sigma field modifiers and regex patterns
Assets
Common Detection Patterns
Pattern 1: Process Execution Monitoring Detect suspicious process creation with command-line analysis:
logsource:
category: process_creation
product: windows
detection:
selection:
Image|endswith:
- '\powershell.exe'
- '\cmd.exe'
CommandLine|contains:
- 'Invoke-'
- 'IEX'
- 'FromBase64String'
Pattern 2: Network Connection Monitoring Detect suspicious outbound connections:
logsource:
category: network_connection
product: windows
detection:
selection:
Initiated: 'true'
DestinationPort:
- 4444
- 5555
- 8080
filter:
DestinationIp|startswith:
- '10.'
- '172.16.'
- '192.168.'
condition: selection and not filter
Pattern 3: File Event Monitoring Detect file creation in suspicious locations:
logsource:
category: file_event
product: windows
detection:
selection:
TargetFilename|contains:
- '\Windows\Temp\'
- '\AppData\Roaming\'
TargetFilename|endswith:
- '.exe'
- '.dll'
- '.ps1'
Integration Points
CI/CD Integration Build detection-as-code pipelines:
name: Sigma Rule Validation
on: [push , pull_request ]
jobs:
validate:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v2
- name: Validate Sigma Rules
run: |
pip install pysigma
python scripts/sigma_validate.py --directory rules/
- name: Convert to Production Format
run: |
python scripts/sigma_convert.py --directory rules/ --backend splunk --output converted/
SIEM Deployment Automated rule deployment:
Splunk: Use Splunk REST API or splunk-sdk for savedsearches
Elasticsearch: Convert to EQL and deploy via Kibana API
Microsoft Sentinel: Convert to KQL and deploy via Azure API
QRadar: Convert to AQL and deploy via QRadar API
Threat Intelligence Integration Enrich rules with threat intel:
Tag rules with threat actor TTPs
Reference threat reports and IOCs
Map to MITRE ATT&CK techniques
Track rule effectiveness against known threats
Troubleshooting
Issue: Conversion Fails for Specific Backend Solution : Check backend compatibility and field mappings. Some backends have limitations:
Review references/backend-support.md for known limitations
Use sigma_convert.py --backend <backend> --debug for detailed error output
Check if field names are supported in target backend
Consider custom pipeline transformations for unsupported fields
Issue: High False Positive Rate Solution : Refine detection logic with additional filters:
Review false positive patterns
Add exclusion filters for legitimate use cases
Use more specific field modifiers (e.g., |endswith vs |contains)
Consider time-based correlation for behavioral detection
Test with historical data to validate tuning
Issue: Rule Not Triggering in Target SIEM Solution : Verify log source availability and field mappings:
Confirm log source is ingested: Check SIEM data sources
Verify field names match: Use sigma_convert.py --show-fields to see mapping
Test converted query directly in SIEM
Check for case sensitivity issues in field values
Validate time window and search scope in SIEM
MITRE ATT&CK Integration Tag rules with ATT&CK tactics and techniques:
tags:
- attack.execution
- attack.t1059.001
- attack.defense_evasion
- attack.t1027
attack.initial_accessattack.executionattack.persistenceattack.privilege_escalationattack.defense_evasionattack.credential_accessattack.discoveryattack.lateral_movementattack.collectionattack.exfiltrationattack.command_and_controlattack.impact
Best Practices
Start with Community Rules : Use SigmaHQ repository (3000+ peer-reviewed rules) as foundationVersion Control : Store rules in Git with meaningful commit messagesTest Before Deploy : Validate against historical data in test environmentDocument Tuning : Track false positive patterns and tuning decisionsMap to Frameworks : Tag all rules with MITRE ATT&CK and compliance mappingsAutomate Validation : Use CI/CD to validate rules on every changeMonitor Effectiveness : Track rule trigger rates and true positive ratesRegular Updates : Review and update rules based on new threat intelligence
References 