Top 5 Best Free and Open-Source SIEM Tools


In this article, we will take a look at Top 5 Best Free and Open-Source SIEM Tools that are in the market that you can pick and use it in your enterprise that you can use as proper Security Information and Event Management (SIEM) solution.

And we will cover what is in the market now in the category of SIEM Solutions and which one is the best one that covers all your basic needs.

What is Open Source SIEM? 

Basically what Open Source means in simple terms is that the complete source code of any application that has an Open Source license. That is really helpful in understanding the application and do modification based on your requirements without having the fear of copyright.

Similarly, an Open Source SIEM means that the whole Security Information and Event Management solution has its source code available for public use. As these tools are free to use and businesses can save the heavy costing that most of the paid SIEM solutions provide and still getting almost the same visibility on their infrastructure.

While free SIEM tools can’t provide the comprehensiveness of enterprise-level solutions, open-source SIEM does offer solid functionality at an affordable rate. Significantly, these free SIEM tools don’t impose limits on the data it utilizes or retains.  This makes it appealing to small-to-medium-sized businesses (SMBs).

To help to narrow down your search on which open-source SIEM solution we are giving the list of Top 5 Best Free and Open-Source SIEM Tools.

1.AlienVault OSSIM:

AlienVault OSSIM

AlienVault OSSIM is the Open-Source version of their premium product AlienVault USM, which is one of the leading commercial SIEM solutions. OSSIM is more of a framework that consists of many open source security projects all included in one place like Snort, Nagios, OSSEC, and OpenVAS. You can pretty much monitor all the devices using the AlienVault Agent that is used to send data log to OSSIM to Syslog or GELF endpoint or it can directly take input by integrating OSSIM with CloudFlare and Okta.

As it is an open-source solution it lacks many of the features that are found in it paid version USM like Log Management, Cloud infrastructure monitoring, Security automation, continuously updated threat information, and visualization. Deployments are limited to a single server, making OSSIM difficult to scale. OSSIM is useful for evaluating USM or learning more about SIEM in general, but less as a production solution.


  • Built on proven open source projects.
  • A large community of users and developers.


  • On-premise monitoring only. Does not support cloud platforms such as AWS and Azure.
  • No log management, visualizations, automation, or third-party integrations.
  • Single-server architecture.

2.The ELK Stack SIEM:

The ELK Stack SIEM

The ELK Stack is arguably the most popular open-source SIEM tool available, but like Snort and OSSC there is room for debate about whether or not it qualifies as a SIEM or not on its own.

The ELK stack consists of open-source products like Elasticsearch, Logstash, and Kibana. Logstash is the receiver for logs and data from almost any source. It can filter, process, correlate and can enhance any log data that it encounters.

Elasticsearch is the storage engine and one of the best solutions in its field for storing and indexing time-series data. Kibana is the visualization layer in the stack and an extremely powerful one at that. Beats include a variety of light-weight log shippers that are responsible for collecting the data and shipping it into the stack via Logstash.

Logstash uses a wide array of input plugins to collect logs. However, it can also accept input from more purpose-built solutions like OSSEC or Snort. Combined, the ELK Stack’s log processing, storage, and visualization capabilities are functionally unmatched. For the purposes of SIEM however, the ELK Stack — at least in its raw open-source format, is missing some key components.



OSSEC is the most popular host-based intrusion detection system (IDS) that works with Linux, Windows, macOS, and Solaris, as well as OpenBSD and FreeBSD. OSSEC consists of two main components one the host agent (responsible for collecting the logs) and the main OSSEC application that processes all the log details.

It also has a GUI that has been deprecated but as there are other open-source solutions that do a better job at data visualization it is recommended that you use those solutions for data visualization some of the tools are Kibana and Grafana.

OSSEC directly monitors and log the number of parameters on the host. That include log files, file integrity, rootkit detection, and Windows registry monitoring.

OSSEC also can perform log analysis from other network services, including most of the popular open-source FTP, mail, DNS, database, web, firewall, and network-based IDS solutions. OSSEC can also analyze logs from a number of commercial network services and security solutions.

Whether or not OSSEC can be counted as an “all in one” SIEM system is debatable. OSSEC definitely does the hard work involved in implementing a SIEM system: it collects data and analyzes it, but lacks some of the core log management and analysis components required. It’s worth pointing out that the OSSEC project has been forked by other HIDS solutions (e.g. Wazuh) that extend OSSEC functionality and make it a more complete SIEM option.


Snort is a very popular network-based IDS solution. There is a major difference between network-based IDS and a host-based IDS system, the main difference between both is that while a host-based IDS monitors a single computer, server or endpoint, the network-based IDS goes further than that into the network and scan all the traffic that they can see.

The main purpose of network-based IDS systems is to sniff, log and perform real-time analysis on the network flow to identify anomalies. It can display real-time packet streams to a console, dump them to log files or analyze them.

Snort mostly relies on its plugins to determine how and where to store all the log that it generates. Snort can either store all the logs in a plain text file or to a database on pager or any other destination.

There are different built-in filters that Snort provided and can be used to filter out the traffic that you don’t want Snort to sniff and store in the logs and you don’t have to display that or analyze all packets traversing a network link. It can restrict itself to information pertaining to a specific host or matching specific patterns—something that is of increasing utility as network throughput of 100Gbps on individual network links becomes more common.

It can also generate alerts based on specific patterns that are identified in the network traffic and send those alerts on phone number or any relevant method that is configured for that.

But same as with OSSEC we have to use some other opensource solutions for visualizations. It is not unusual to see Snort and OSSEC working together to each fill different niches in the grand scheme of data center SIEM needs.

Suricata is a competing open source network-based IDS that is frequently used in place of Snort.



Wazuh began as a fork of OSSEC, one of the most popular open-source SIEMs. It has since grown to become its own unique solution with new features, bug fixes, and more optimized architecture.

Wazuh is built on the Elastic Stack (Elasticsearch, Logstash, and Kibana) and supports both agent-based data collection, as well as Syslog ingestion. This makes it effective for monitoring devices that generate logs but don’t support a full agent, such as network devices or printers. Since Wazuh and OSSEC share a common code base, Wazuh supports existing OSSEC agents and even provides a migration guide for migrating from OSSEC to Wazuh.

Also Read: How to Setup Wazuh Open Source SIEM Virtual Machine

While OSSEC is still being actively maintained, Wazuh is seen as a continuation of OSSEC due to its addition of a new web UI, REST API, more comprehensive ruleset, and many other improvements.


  • Based on (and compatible with) OSSEC.
  • Supports Docker, Puppet, Chef, and Ansible deployments.
  • Supports cloud infrastructure monitoring including AWS and Azure.
  • Comprehensive ruleset that detects many common attack types and includes compliance mapping with PCI DSS v3.1 and CIS.
  • Integrates with Splunk for visualizing alerts and API data.


  • Somewhat complicated architecture: requires a complete Elastic Stack deployment in addition to Wazuh server components.