The top free and open source SIEM tools for 2025

Security Information and Event Management (SIEM) tools are foundational components of modern cybersecurity infrastructure. They serve as centralized platforms for collecting, analyzing, and managing security-related data from across an organization’s IT environment.

This includes:

• network devices
• servers
• endpoint
• applications
• cloud services

By aggregating and correlating this vast amount of information, SIEM tools provide crucial visibility into security events, enabling proactive threat detection, efficient incident response, and compliance management.

Free SIEM tools offer significant advantages for cybersecurity professionals, particularly those in organizations with budget constraints or those looking to gain hands-on experience with SIEM or SIEM-like technologies. These tools can provide a cost-effective way to implement essential security monitoring capabilities, enhance threat detection, and improve incident response without the significant financial investment that’s often associated with commercial solutions.

They can also often foster a strong sense of community and provide opportunities for learning and collaboration. Furthermore, the open-source nature of many free SIEMs allows for customization and integration with other security tools, providing flexibility to tailor the solution to specific organizational needs.

Here are 10 noteworthy open-source and free SIEM—and SIEM-adjacent—tools available in 2025:

Wazuh

Emerging in 2015 as a powerful and versatile open-source security monitoring solution, Wazuh extends beyond traditional SIEM functionalities by incorporating endpoint detection and response (EDR) capabilities. It performs in-depth log analysis, monitors file integrity to detect unauthorized changes, identifies intrusions through signature and anomaly detection, and assesses systems for known vulnerabilities.

Its agent-based architecture allows for comprehensive monitoring of endpoints across diverse operating systems. Wazuh’s integration with Elastic Stack, a tool that we’ll touch on later, provides robust search, analysis, and visualization capabilities, making it a compelling choice for organizations seeking a holistic security monitoring platform without licensing fees. Its active community also ensures ongoing development and support.

Security Onion

This free and open-source Linux distribution is purpose-built for threat hunting, enterprise security monitoring, and comprehensive log management. Available on GitHub, it bundles a suite of leading security tools, including a handful we mention here, including Elastic Stack, Suricata, and Kibana. It also includes osquery, CyberChef, and Zeek (formerly Bro, a powerful network analysis framework).

Security Onion simplifies the deployment and management of these tools through a unified interface and pre-configured dashboards. Its focus on network security monitoring, combined with robust log analysis capabilities, makes it particularly helpful for organizations seeking deep visibility into their network traffic and security events. The active community provides extensive documentation and support.

OSSEC

A well-established and mature open-source host-based intrusion detection system (HIDS), OSSEC also offers significant log management and real-time event analysis features. It excels at monitoring individual hosts for malicious activity, including log file analysis, file integrity checking to detect tampering, rootkit detection, and monitoring critical Windows registry keys.

Atomicorp, an OSSEC dashboard graphical user interface (GUI) can help collect, categorize, and understand SIEM data from different logs—OSSEC can analyze logs from a wide array of operating systems, applications, and security devices. Its active response capabilities allow for automated actions in response to detected threats. While primarily a host-focused intrusion detection system, its log analysis capabilities contribute significantly to overall security monitoring.

OpenSearch

Originating as a fork of the popular Elasticsearch and Kibana projects, OpenSearch is an open source search and analytics suite that serves as a strong foundation for building a free SIEM. While not a complete SIEM out of the box, it can serve as the core of a SIEM; its powerful search engine and the associated OpenSearch Dashboards for visualization make it highly adaptable for security data analysis.

When integrated with open source log shippers and correlation engines, OpenSearch provides a scalable and flexible platform for security event indexing, searching, and visualization. Its open and permissive licensing makes it attractive for organizations seeking to avoid restrictive licensing models.

Elastic Stack

Comprising Elasticsearch, Logstash, and Kibana, Elastic Stack (formerly known as the ELK Stack) has historically been a cornerstone of many open-source SIEM deployments. Elasticsearch provides a distributed search and analytics engine, Logstash handles log aggregation and processing from various sources, and Kibana offers a rich interface for data visualization and exploration.

While the licensing terms for the default distribution have changed, making the “free” aspect more nuanced for commercial deployments, the core technologies remain open source, widely used and the basis of numerous SIEM solutions. While Elastic Stack can require a great deal of overhead, its flexibility and powerful analytical capabilities make it a valuable toolset for those willing to invest the effort in configuration and integration.

Graylog

This open source log management and analysis platform offers a user-friendly web interface and robust capabilities for collecting, indexing, and analyzing log data. While Graylog also has commercial offerings with advanced features, the open-source version, Graylog Open, provides a solid foundation for building SIEM functionality.

Its intuitive interface and powerful search and alerting capabilities make it accessible to a wider range of users. Graylog’s extensibility through plugins allows for integration with various data sources and security tools, enhancing its SIEM capabilities.

UTMStack

This open source unified threat management (the UTM in UTMStack) platform integrates various security functions like firewall, intrusion detection and prevention, and virtual private networks (VPN), providing centralized logging across these layers.

While not a traditional SIEM, its aggregation of security events from multiple integrated tools offers a holistic view of network security activity, making it a valuable free option for organizations seeking integrated security monitoring and analysis capabilities without the complexity of deploying separate systems.

Prelude

This open source SIEM framework distinguishes itself by focusing on event correlation and forensic analysis. It is designed to receive and process security alerts in the standardized intrusion detection message exchange format (IDMEF). Prelude can integrate with other open source security tools, such as OSSEC and Snort, to centralize and correlate security events from different sources.

While the open-source version might have limitations in scalability and advanced features compared to its commercial offering, it provides a standards-based approach to SIEM and can be beneficial for organizations prioritizing interoperability.

Snort

While not a SIEM tool—it’s primarily known as a network intrusion detection system (IDS)—Snort can also contribute to SIEM capabilities by generating detailed logs of network traffic and detected threats. These logs can then be ingested and analyzed by other SIEM tools, such as Elastic Stack or Wazuh, to provide network-based security insights. Snort’s rule-based detection engine and active community support make it a valuable component of a broader security monitoring strategy.

Established in 1998, Snort has had an enduring legacy in network security. Before Snort, IDS solutions were expensive; Snort’s open-source nature lowered the barrier to entry for many, especially those with lower budgets, to bolster their security.

Suricata

Similar to Snort, Suricata is a high-performance, open source intrusion detection and prevention system (IDPS) and network security monitoring engine. It offers multi-threading capabilities for improved performance and supports various detection rules and signature languages.

Suricata’s ability to analyze network traffic in real-time and generate detailed logs makes it a valuable data source for SIEM analysis, providing critical visibility into network-based threats and anomalies.

At their core, SIEM tools possess several key features and capabilities designed to help defenders protect systems by providing a centralized platform for security visibility and analysis:

• Log management: This involves the centralized collection, normalization, and storage of logs from diverse sources. Efficient log management ensures that security-relevant data is readily available for analysis and investigation. The ability to handle large volumes of data and retain it for specified periods is critical for both security analysis and regulatory compliance.
• Threat detection: SIEMs employ various techniques to identify potential security threats. This includes rule-based correlation, where predefined patterns of events trigger alerts. More advanced SIEMs incorporate behavioral analytics, which establish baselines of normal activity and flag deviations that could indicate malicious behavior. Threat intelligence feeds, providing up-to-date information on known threats and indicators of compromise (IOCs), are often integrated to enhance detection capabilities.
• Incident response: When a security incident is detected, the SIEM plays a vital role in the response process. It provides context around the incident by consolidating relevant logs and alerts. This allows security teams to understand the scope and impact of the incident more quickly. Many SIEMs offer features to facilitate incident response workflows, such as automated alert escalation, case management, and integration with other security tools for remediation.
• Compliance management: Organizations are often required to comply with various regulatory frameworks (e.g., GDPR, HIPAA, PCI DSS). SIEM tools aid in compliance efforts by providing the necessary logging and reporting capabilities to demonstrate adherence to these standards. They can generate reports on access controls, data modifications, and other security-relevant activities.
• Security analytics: Beyond basic threat detection, SIEMs enable security analysts to perform in-depth investigations and identify trends. Features like data visualization, search and filtering capabilities, and the ability to create custom dashboards are essential for gaining meaningful insights from the collected data.

Effectively implementing and utilizing free SIEM tools requires careful planning and consistent effort. Here are some key pieces of advice:

• Proper configuration: Accurate and thorough configuration is paramount. This includes correctly configuring log sources to ensure all relevant data is being collected, fine-tuning detection rules to minimize false positives and negatives, and properly setting up alert mechanisms. Invest time in understanding the configuration options of your chosen SIEM tool and tailor them to your specific environment and security requirements.
• Regular updates and patching: Like any software, SIEM tools require regular updates and patching to address security vulnerabilities and ensure optimal performance. Stay informed about new releases and security advisories for your chosen tool and establish a process for applying updates promptly.
• Log source management: Identify and onboard all relevant log sources. This may include operating systems, network devices (firewalls, routers, switches), applications, databases, and cloud services. Ensure that logs are being collected in a consistent format and that time synchronization across all devices is properly configured for accurate event correlation.
• Rule and alert management: Start with a baseline set of detection rules and gradually customize them based on your organization’s specific threat landscape and risk profile. Regularly review and tune alert thresholds to reduce noise and focus on genuine security incidents. Implement a clear process for triaging and responding to alerts generated by the SIEM.
• Data retention policies: Define clear data retention policies based on your organizational requirements and any applicable compliance regulations. Ensure that your SIEM has sufficient storage capacity to accommodate the defined retention period.
• Integration with other security tools: Explore opportunities to integrate your free SIEM with other security tools in your environment, such as vulnerability scanners, threat intelligence platforms, and ticketing systems. This can enhance the overall effectiveness of your security posture and streamline incident response workflows.

To maximize the value of free SIEM tools, consider the following suggestions:

• Utilize community support and resources: Open source SIEM tools often have vibrant and active communities. Leverage forums, mailing lists, and online documentation to seek assistance, share knowledge, and learn best practices from other users. These communities can be invaluable resources for troubleshooting issues and understanding advanced features.
• Thorough documentation: Maintain comprehensive documentation of your SIEM deployment, including configuration settings, integration details, custom rules, and incident response procedures. This will be crucial for troubleshooting, knowledge sharing within your team, and ensuring the long-term maintainability of your SIEM.
• Continuous learning and training: Cybersecurity is a constantly evolving field. Invest in continuous learning and training for your security team on how to effectively use and manage your chosen SIEM tool. This includes understanding its features, developing effective search queries, and conducting thorough security investigations.
• Start small and iterate: If you are new to SIEM, consider starting with a limited scope and gradually expanding your deployment as your understanding and confidence grow. Begin by monitoring critical systems and applications and progressively onboard additional log sources.
• Contribute back to the community (if possible): If you have the technical expertise, consider contributing back to the open source community by reporting bugs, submitting patches, or sharing your knowledge and experiences. This helps to strengthen the community and improve the tool for everyone.

Utilizing a SIEM tool is important for effective cybersecurity in today’s complex digital environment. They provide the essential visibility and analytical capabilities needed to detect threats, respond to incidents, and maintain compliance. While commercial SIEM solutions offer advanced features and enterprise-level support, the landscape of free and open source SIEM tools has matured significantly.

Options like Wazuh, Security Onion, and Elastic Stack provide robust functionalities that can be highly beneficial for organizations with limited budgets or those seeking greater control and customization. By carefully selecting the right tool, implementing it effectively, and actively engaging with the community, organizations can significantly enhance their security posture without incurring substantial licensing costs. The key lies in understanding the capabilities of these free tools and dedicating the necessary resources to proper configuration, ongoing maintenance, and continuous learning.

Download Red Canary’s guide to evaluating managed detection and response (MDR) and SIEM to learn the benefits of both and how to find out which one is right for your organization.