Key Takeaways
- Open-source SIEM removes the licence, not the cost. You save the per-gigabyte fee, but storage, infrastructure and analyst time to tune and run it remain real costs.
- Wazuh is the most widely adopted open-source SIEM in 2026, combining SIEM and XDR with unlimited self-hosted agents and strong compliance reporting.
- Security Onion is the go-to for network-centric monitoring, bundling Suricata, Zeek and other tools for deep network visibility.
- Graylog Open excels at log-centric work and search, while Elastic Security builds detection on the Elastic Stack with an EDR component.
- The best choice depends on your priority: endpoint and compliance (Wazuh), network detection (Security Onion), log management (Graylog) or Elastic-native analytics (Elastic Security).
Why Teams Choose Open-Source SIEM
The number one reason is cost. Commercial SIEM platforms are almost always priced on the volume of data you ingest, so as logging grows the bill climbs steeply, and organisations find themselves dropping log sources to control spend, which is the opposite of what good security needs. Open-source SIEM removes the licence fee entirely, letting you collect the logs you should collect rather than the logs you can afford.
The second reason is control and transparency. Open source means no black-box detection logic, no vendor lock-in, and the freedom to extend, integrate and self-host on your own terms. For organisations with data-residency requirements across India, Singapore, UAE or Malaysia, self-hosting is often a compliance advantage in itself.
Wazuh: The Most Widely Adopted
Wazuh is consistently the most recommended open-source SIEM in 2026, and for good reason. It is free and open source, supports unlimited agents when self-hosted, and combines SIEM and XDR capabilities in one platform. Beyond log collection and correlation, Wazuh brings file integrity monitoring, vulnerability detection, security configuration assessment against CIS benchmarks, and active response that can act on endpoints automatically.
Its compliance reporting (PCI DSS, HIPAA, ISO 27001 and more) and broad integration with cloud platforms make it a strong fit for organisations that need both threat detection and audit evidence. The trade-off, noted even by competitors, is that getting the most out of Wazuh takes tuning and detection engineering effort. It is powerful out of the box but rewards investment in custom rules and decoders. This is the platform Codesecure builds most of its SOC engagements on.
Thinking About a SOC or SIEM Programme?
Codesecure builds and runs open-source SOC and SIEM platforms on Wazuh, TheHive, Cortex, MISP and n8n for businesses across India, Singapore, UAE and Malaysia. ISO/IEC 27001:2022 certified delivery, named OSCP, CEH and CISSP consultants, fixed-price proposals and no vendor lock-in.
See SOC and SIEM Services →Security Onion: Network-Centric Monitoring
Security Onion is the open-source choice when network visibility is the priority. Rather than a single engine, it bundles a suite of best-in-class open tools, including Suricata and Zeek for network intrusion detection and traffic analysis, and integrates with host-based detection to give combined network and endpoint coverage.
It suits teams that want deep packet and flow-level insight, threat hunting across network data, and a ready-made distribution that saves assembling the components yourself. The cost is that network monitoring at scale is storage- and compute-heavy, and tuning network detections to your environment is specialist work.
Graylog and Elastic Security
Graylog Open is built around log management and fast search. It provides many SIEM-adjacent capabilities, strong parsing and a clean interface, and suits smaller teams that want broad log visibility and flexible search without heavy licensing. Security-specific detection content is lighter than Wazuh's, so it is often chosen where log centralisation is the main goal.
Elastic Security builds detection on the widely used Elastic Stack (Elasticsearch, Kibana) and ships with an endpoint agent (Elastic Defend) alongside its SIEM detection rules. Teams already invested in Elastic for logging or observability often extend it into security. The open tier is capable, though some advanced features sit behind paid subscriptions, so read the licensing carefully before committing.
OSSIM and Other Options
OSSIM (the open-source edition of AlienVault) is a long-standing name that bundles asset discovery, vulnerability assessment and correlation. It remains in use, but development momentum and community energy have shifted toward the platforms above, so weigh its roadmap before building on it.
Other names appear in comparisons, including Prelude and Apache Metron, but community support and real-world adoption for these are thinner. For a new deployment in 2026, the mainstream, well-supported choices are Wazuh, Security Onion, Graylog and Elastic Security. Be wary of listicles that pad their numbers with abandoned or mislabelled projects; healthy community and active development matter more than a long feature table.
Not Sure What You Actually Need?
SIEM, managed SOC, MDR, co-managed detection: the right answer depends on your team, your logs and your compliance drivers. Our SOC lead will walk through your environment on a 30-minute free scoping call, with no obligation and no slideware.
Book a Free Scoping Call →How to Choose the Right One
Match the tool to your primary need. If you want broad coverage, endpoint telemetry, compliance reporting and XDR in one platform, Wazuh is the default recommendation. If your priority is deep network detection and hunting, Security Onion. If it is log centralisation and search above all, Graylog. If you already run the Elastic Stack, Elastic Security is the natural extension.
Whichever you choose, plan honestly for the parts that are not free: storage and retention, the compute to run the indexer and collectors, and above all the people to tune rules, reduce false positives and respond to alerts. A free SIEM that nobody operates protects nobody. Many organisations deploy the open-source platform and pair it with a managed or co-managed SOC so the tooling cost stays near zero while the operations are covered by experts.
Frequently Asked Questions
What is the best open-source SIEM in 2026?
Wazuh is the most widely adopted and most commonly recommended open-source SIEM in 2026. It combines SIEM and XDR capabilities, supports unlimited self-hosted agents, and includes file integrity monitoring, vulnerability detection and compliance reporting. The best choice for you, though, depends on your priority: Security Onion leads for network monitoring and Graylog for log management.
Is open-source SIEM really free?
The software licence is free, but running it is not. You still pay for storage and retention, the compute to run the indexer and collectors, and, most significantly, the skilled staff to tune rules and operate the platform. Open source removes the per-gigabyte licence that dominates commercial SIEM pricing, which is a large saving, but it does not remove operational cost.
Is Wazuh a SIEM or an XDR?
Both. Wazuh is an open-source platform that combines SIEM capabilities (log collection, correlation, alerting and compliance reporting) with XDR capabilities (endpoint telemetry, threat detection and active response). This combination in a single free, self-hostable tool is a big part of why it is so widely adopted.
What is the difference between Wazuh and Security Onion?
Wazuh is endpoint- and compliance-centric, with agents on hosts delivering file integrity monitoring, vulnerability detection and active response, plus strong compliance reporting. Security Onion is network-centric, bundling tools like Suricata and Zeek for deep network intrusion detection and traffic analysis. Many mature SOCs use both together for combined host and network visibility.
Can open-source SIEM meet compliance requirements like PCI DSS or ISO 27001?
Yes. Wazuh in particular ships compliance reporting for PCI DSS, HIPAA, ISO 27001 and other frameworks, and open-source SIEM can satisfy the log collection, retention and monitoring controls these frameworks require. The key is configuring retention and review correctly and keeping evidence of monitoring, which is where expert setup helps.
Can Codesecure deploy and run an open-source SIEM for us?
Yes. Codesecure specialises in open-source SOC and SIEM built on Wazuh, TheHive, Cortex, MISP and n8n, and can deploy, tune and run it as a managed or co-managed service. You get the platform with no per-gigabyte licence and the operations covered by named OSCP, CEH and CISSP consultants across India, Singapore, UAE and Malaysia.
Deploy A Free SIEM, Backed By People Who Run It Daily
Codesecure builds and operates open-source SIEM on Wazuh, Security Onion and the wider open stack, tuned to your environment and your compliance needs. Keep tooling cost near zero and let named OSCP, CEH and CISSP consultants handle the detection engineering and response.
