Best Free and Open-Source SIEM Software in 2020

By gns3-reviews on January 28, 2020

For IT teams looking to update their cybersecurity strategy, SIEM tools can deliver end-to-end visibility to help you stay on top of a wide range of threats.

In this article, I’m going to focus on my favorite enterprise-grade SIEM products. The products I’ll look at either offer free, fully functional trials to give you a taste of what kind of functionality you’ll get should you invest in the full product, or they’re free altogether. Regardless of which category you’re most interested in, consider which tools will add value to your cybersecurity efforts in the long run. By taking the time to make the right choice, you can empower your team to counter the worst out there.

Best Free Trial SIEM Software

  1. SolarWinds Security Event Manager (SEM)

SolarWinds® Security Event Manager combines top-of-the-line security capabilities with the event logging, compliance reporting, and performance support functionalities essential for business IT teams. SEM is an all-purpose option for companies looking for a comprehensive SIEM tool, with an added focus on HIPAA, PCI DSS, and SOX compliance.


With SEM, IT professionals get a tool that implements smoothly, with automated parameters designed to protect against hundreds of threats. In addition, SEM offers a powerful search function to make log analysis straightforward and strategic. Thanks to the 30-day free trial from SolarWinds, teams can take the time to learn whether this software is right for them.

  1. SolarWinds Threat Monitor

Threat Monitor is another favorite of mine from SolarWinds. Alongside the trademark support and expertise from a leader in the market, this product offers powerful SIEM capabilities with an emphasis on security. Threat Monitor helps IT professionals protect their digital environment with advanced intrusion detection capabilities, regularly updated threat assessments, and near-real-time vulnerability checks—all included in the free trial.

SolarWinds Threat Monitor

In addition to compliance reporting and helpful search functionality, Threat Monitor delivers a wealth of automated responses—especially compared with other SIEM tools. Because Threat Monitor is cloud-based, IT teams get to deploy powerful cybersecurity defenses without a resource-intensive footprint.

Top Free and Open-Source SIEM Tools

  1. OSSIM

With OSSIM, users get a powerful SIEM open-source tool with the logging and monitoring elements of SEM and the threat assessment, automated responses, and data synthesis of SIM.

That said, the tool has potential drawbacks. IT professionals have noted the difficult setup process and the intensive upfront labor required to customize it. Additionally, support from OSSIM can cost you, making paid tools a possibly wiser move.

  1. Splunk Free

In terms of functionality and usability, Splunk’s complete product is a workhorse in the SIEM market. Splunk delivers end-to-end visibility over even the most complex digital environments and is surprisingly easy to navigate despite the full range of complex tools it offers.

While the full version of Splunk is a great option, the free version of the software is still useful. It comes with the limitation of indexing only 500MB per day, which means it won’t be a one-size-fits-all solution for every business.

  1. OSSEC

Available for Mac OS, Linux, Solaris, and BSD, OSSEC is an SIEM open-source tool focused on intrusion detection. Personally, I like this product’s log analysis functionality, which covers FTP, mail servers, and databases. OSSEC also excels when it comes to monitoring more than one network from a single point.

However, I’d be remiss not to highlight a few of its cons. For one, using it on Windows requires using the server-agent mode. Additionally, some users have noted issues with updates, such as the tool reverting to its original settings after any kind of patch.

  1. Snort

An intrusion detection and prevention tool available on Windows and Linux, Snort has become a popular option for IT professionals looking for an effective free SIEM tool. Snort keeps an eye on network traffic, puts your team’s rules in practice, and does so without too much else to get in the way.

This is not a complete SIEM offering. If these discrete functions sound useful to you, then Snort can certainly deliver. However, other options on this list provide more horsepower in terms of network logging and monitoring.

  1. Elasticsearch

A package of software offerings, Elasticsearch gives teams a powerful suite of utilities for SIEM purposes. For example, the Beats platform provides easy data shippers and collectors, Logstash analyzes data and support plug-ins, Kibana delivers visualization, and Elasticsearch acts as the search engine making it possible to explore data.

This tool has its limitations. It lacks strong correlation capabilities, offers no out-of-the-box alerts, and can’t perform incident management.

The Importance of SIEM Software

Security information and event management (SIEM) tools have become a top priority for IT teams. By aggregating relevant information and identifying potentially critical events, organizations can centralize the cybersecurity process and take a more proactive, rather than reactive, approach to keeping their digital infrastructure safe. As the range of bad actors and potential attack vectors widens and complexifies, this kind of strategy is a must.

Essential Capabilities of SIEM Software

SIEM unifies what were once disparate aspects of cybersecurity management: security information management (SIM) and security event management (SEM). SIM technology records, analyzes, and synthesizes log data, while its SEM counterpart monitors events and generates alerts for potential incidents. Together, they help IT teams develop and act on a real-time understanding of their IT landscape.

I have based my review of the top free SIEM tools on certain criteria I consider essential. With these key criteria in mind, you should be equipped to figure out exactly what kind of tool you need. The ideal SIEM tool will perform the following functionalities:

  • Log Events

This is an essential part of any good SIEM tool. By collecting relevant events on your network, event logging allows teams to identify real-time issues and look into them before they spread.

  • Detect Intruders

Your SIEM tool should do more than track what’s going on in your network; it should also analyze data on an ongoing basis. By contextualizing issues, intrusion detection utilities can help organizations act with better information.

  • Send Alerts

In addition to analyzing logs and detecting intrusion attempts, SIEM products should automatically alert the right network officials when they might need to act.

  • Detect AI-Powered Threats

By synthesizing streams of information from across your network and making sense of recent threats, the best SIEM tools can anticipate future threats—including “smart” threats—and help you respond to them faster.

  • Filter and Store Data

To make archived information and logs useful, SIEM tools need to provide mechanisms for filtering data. This allows users to investigate issues as quickly and strategically as possible.

  • Visualize Data

Either as a key part of your SIEM tool or as a supported integration, the ability to visualize data and threat assessments is a must. By analyzing graphs updated in real time, you can access at-a-glance understandings of your network.

  • Integrate with Existing Systems

The right SIEM tool for your organization will integrate easily with your existing network and be able to map ongoing events.

  • Support Compliance

While this may vary from one industry to the next, SIEM software should support compliance monitoring and reporting.

How SolarWinds Security Event Manager Delivers

Organizations trying out SIEM software for the first time often opt for free or open-source tools. This is clearly a cheaper option, but in my experience, it’s usually a temporary one. For businesses facing a legitimate number of cybersecurity threats, free SIEM products may not provide the kind of long-term protection needed.

The right SIEM tool for your organization should deliver comprehensive monitoring and protection for your network—in both the short and long runs—with a streamlined and intuitive user experience. If your team is just beginning to look into SIEM solutions, free open-source SIEM tools can act as a solid introduction to what this kind of software can do for your digital environment.

However, if you’re ready to invest in an enterprise-grade SIEM solution, my ultimate recommendation goes to SolarWinds Security Event Manager. As a comprehensive security event management tool with a focus on logging and compliance, SEM gives IT teams a wide range of critical capabilities at a time when cybersecurity has never been more important.

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