Top Open Source SIEM Tools in 2025

In today's complex digital landscape, security threats are increasingly sophisticated. Organizations need robust Security Information and Event Management (SIEM) solutions to detect, analyze, and respond to incidents effectively. While commercial platforms like Splunk or LogRhythm offer comprehensive features, their costs can be prohibitive, especially for small to medium-sized organizations.

Open source SIEM tools provide a compelling alternative. By 2025, these solutions have matured significantly, delivering powerful capabilities without the high price tag. This post explores the top open source SIEM tools available this year.

What Makes a Good SIEM Solution?

A comprehensive SIEM solution should include:

Log Collection: Gathering logs from diverse sources
Data Normalization: Standardizing log formats for analysis
Correlation: Identifying patterns across events
Alerting: Notifying teams of suspicious activities
Visualization: Providing dashboards for insights and reporting
Threat Intelligence: Incorporating up-to-date threat data
Compliance Support: Enabling regulatory reporting and controls

No single open source tool offers all these features out of the box, so organizations often combine multiple tools to build a complete SIEM stack.

Top Open Source SIEM Tools in 2025

1. Wazuh

https://wazuh.com/

Wazuh is a leading open source security platform in 2025, evolving from its OSSEC roots into a comprehensive monitoring solution.

✨ Key Features:

Host-based intrusion detection (HIDS)
Log data analysis and file integrity monitoring
Vulnerability detection and configuration assessment
Cloud security monitoring (AWS, Azure, Google Cloud)
Compliance monitoring (PCI DSS, GDPR, HIPAA)
Active response for automated threat mitigation
Integration with OpenSearch for visualization

📌 Wazuh’s unified XDR and SIEM framework offers deep cloud integration and enhanced threat intelligence, providing visibility across hybrid environments—a critical need as hybrid setups dominate.

2. OpenSearch

https://opensearch.org/

OpenSearch, a fork of Elasticsearch and Kibana, is a cornerstone of many SIEM implementations, backed by Amazon’s ongoing development.

✨ Key Features:

Powerful search and analytics engine
Advanced visualization capabilities
Scalable architecture for large datasets
Anomaly detection and machine learning
Alerting and notification systems
Security analytics support

📌 OpenSearch has evolved with SIEM-specific analytics and improved machine learning for anomaly detection. Community-driven security dashboards enhance its utility for security operations.

3. Security Onion

https://securityonionsolutions.com/

Security Onion remains a popular all-in-one Linux distribution, integrating multiple tools for unified security monitoring.

✨ Key Features:

Network security monitoring
Intrusion detection (Suricata, Zeek)
HIDS via Wazuh integration
Log management with OpenSearch
Full packet capture
Traffic analysis tools
Web-based analysis interface

📌 Containerized components improve scalability and performance, while enhanced machine learning and cloud collectors keep it relevant for modern threats.

4. TheHive & Cortex

https://strangebee.com/cortex/

TheHive is a robust open source incident response platform, complemented by Cortex for automation, fitting seamlessly into SIEM ecosystems. Together, they streamline incident management and response.

✨ Key Features:

Case management for incidents
Integration with security tools
Collaborative investigation features
Automated responses via Cortex
Customizable dashboards
API-first design

📌 TheHive orchestrates incident response workflows, while Cortex automates observable analysis (e.g., checking IPs against threat feeds) and response actions like blocking threats. Their tight integration allows security teams to analyze indicators within TheHive cases and act swiftly, reducing manual effort. Expanded integrations with threat intelligence and mature automation workflows enable faster, more effective incident responses.

5. Graylog

https://graylog.org/

Graylog is a powerful log management platform with robust SIEM capabilities.

✨ Key Features:

Scalable log collection
Advanced search functionality
Alerting and dashboards
Role-based access control
Compliance support
Stream processing

Why It’s Great in 2025: Enhanced correlation and threat intelligence integration, paired with a refined UI, make Graylog versatile for organizations of all sizes.

6. Sigma_HQ

https://sigmahq.io/

Sigma_HQ isn’t a SIEM tool but a vital detection component for SIEM systems, providing standardized threat detection rules through the Sigma_HQ ecosystem.

✨ Key Features:

Generic signature format
Extensive threat detection rule database
Conversion for various SIEM platforms
Community-driven rule repository
Tool integration

📌 Sigma Rules, stored and managed via the Sigma_HQ GitHub repository, offer portable detection logic for threats like malware or logon anomalies. Sigma_HQ’s tools convert these rules into SIEM-specific queries, ensuring compatibility across platforms like Elastic or Splunk. With thousands of rules and improved integrations, Sigma simplifies threat detection across diverse SIEM solutions.

7. Malcolm

https://cisagov.github.io/Malcolm/

Malcolm, a newer player, has gained traction as a network-focused SIEM tool.

✨ Key Features:

Network traffic analysis
Integration (Zeek, Suricata)
Full packet capture
Automated alerts
Threat hunting
Visualization and reporting

📌 Its container-based design and enhanced analytics make it a scalable, user-friendly option for network security monitoring.

Building Your Open Source SIEM Stack

Challenges of Open Source SIEM Implementation

Open source SIEMs offer cost benefits but pose challenges:

Integration Complexity: Requires technical expertise
Maintenance Overhead: More effort than commercial options
Limited Support: Relies on community assistance
Performance Tuning: Needs manual optimization
Feature Gaps: May lack some advanced commercial features

The Future of Open Source SIEM

Trends shaping 2025 and beyond include:

AI/ML Integration: Better anomaly detection and automation
Cloud-Native Architectures: Support for containers and serverless
XDR Capabilities: Broader detection and response
Threat Intelligence: Deeper integration
Compliance Automation: Enhanced regulatory support

Conclusion

Open source SIEM tools offer viable alternatives to commercial solutions. Combining these tools creates a powerful, cost-effective security infrastructure. Organizations should assess their needs and capabilities, considering a hybrid approach with commercial tools for optimal balance.