Security Onion has become one of those platforms that anyone setting up or operating a SOC should be familiar with. It's free, open source, and brings together network monitoring, threat hunting, and log management in one place , along with a collection of production-proven tools that accelerate the work of the Blue Team.
Before diving in, it's important to set realistic expectations: it's not a magic bullet or a "fix everything" button . Its power lies in how it integrates multiple components and in the judgment of the team using it. It requires learning how to use it, adapting it to each environment, and maximizing its capabilities; if we do, the platform delivers enormous value.
What is Security Onion and what does it solve?
Security Onion is a Linux distribution specializing in threat detection and response, integrating IDS/IPS, traffic analysis, event management, and more, similar to other security distributions . It's designed for threat hunting, enterprise security monitoring, and log management , with custom interfaces for alerts, dashboards, hunting, PCAP, detections, and case management. It also includes tools such as osquery, CyberChef, Elasticsearch, Logstash, Kibana, Suricata, and Zeek.
Behind the project is Security Onion Solutions, LLC. They create and maintain the platform and fund its development with commercial products and services ; when a company subscribes to their support or pro editions, it contributes to the project's continued evolution in line with the ever-changing threat landscape.
Security Onion Featured Components and Tools
One of its greatest strengths is its selection of built-in engines and utilities ready for correlation. The suite combines packet capture, rule-based IDS, and deep traffic analysis , along with HIDS and a robust search/visualization stack.
Capture traffic with netsniff-ng
Among the components that operate at a low level is netsniff-ng. This component captures traffic and efficiently manages PCAP storage , removing old data when necessary to avoid disk saturation. This capture is essential for reviewing evidence of exfiltration, phishing campaigns, or intrusions that require revisiting the package to understand the what, how, and when.
Rule-based IDS/IPS: Suricata and Snort
Security Onion integrates two veteran signature-based detection tools, both featured on lists of top Linux IDSs : Suricata and Snort. These tools operate using rules that trigger alerts based on known patterns . They rely on "fingerprints" stored in their rule bases and are the first line of defense for detecting malware families, known C2 threats, exploits, and previously described behaviors.
Network analysis with Zeek
In addition to the above, Zeek (formerly Bro) takes a different approach. It performs passive inspection and generates detailed logs of connections (conn, dns, http, ssl/tls, among others). Besides IPs, ports, and protocols, it provides rich attributes such as DNS queries, TLS details, and Layer 7 information for multiple protocols: HTTP, FTP, IRC, SMTP, SSH, SSL, and Syslog, among others.
A practical example of its flexibility: auxiliary sources such as CSV files containing corporate information can be imported and cross-referenced with download events, logins, or other activities. These correlations can then be used to feed antivirus, antimalware, or a SIEM system to orchestrate a more agile response.
HIDS on endpoints with Wazuh
Visibility is further enhanced by a host-based IDS. Wazuh monitors each endpoint with agents for Windows, Linux, and macOS , analyzing system logs, verifying file integrity, monitoring policies, and detecting rootkits. With its real-time alerts and response actions, it adds a proactive layer to your security strategy. It is fully integrated with the Elastic Stack for search and visualization.
Search Stack and Analyst Tools
Security Onion brings Elasticsearch and Kibana for queries and dashboards, along with utilities designed for the analyst's daily work. Sguil acts as a bridge between IDS/IPS and packet capture , accelerating triage and collaborative investigation. Also included are Squert, CapMe, and other proprietary dashboards for hunting, PCAP, and case management.
Other built-in utilities
For rapid analysis and decoding tasks, the platform includes CyberChef. It's the Swiss Army knife for transforming and examining artifacts without leaving the SOC environment. Together with osquery, it allows you to query the entire endpoint pool for states and attributes in bulk.
Meerkat/Snort vs. Zeek: Complementary Approaches
It's important to distinguish between the two most common detection models on the platform. Suricata and Snort trigger rule-based alerts and can passively inspect or block (depending on the deployment), while Zeek prioritizes generating rich telemetry to reconstruct attack narratives. This combination helps both detect known threats and investigate unknown ones.
Visibility and analysis in Security Onion: Sguil, Squert, Kibana and CapMe
A good SOC doesn't just trigger alerts; it needs context, collaboration, and workflow. Sguil's interface centralizes events and allows you to pivot to PCAP to see exactly what happened on the cable. Squert provides agile views, Kibana offers custom searches and dashboards, and CapMe makes it easy to extract relevant packets for a given case.
These integrated views reduce friction between teams: analysts can quickly assign, escalate, and document each incident, avoiding the typical disconnect between detections, searches, and network forensics.
Getting Started with Security Onion: Download, Documentation, and Virtualization
The usual starting point is the official repository. You can download the ISO from GitHub and, before anything else, review the documentation , which includes a very comprehensive "Getting Started" section with several deployment paths.
If you don't have a Linux host available, don't worry: the guide covers virtualization scenarios with VirtualBox and VMware , including creating specific virtual machines to set up the suite and start network audits.
Recommended minimum requirements
To get started on the right foot, the documentation itself suggests a modest base: a 64-bit CPU with two or more cores, 8 GB of RAM, 80 GB of disk space, and a NIC in promiscuous mode . In higher-traffic environments, it's reasonable to increase the RAM to 16 GB or more and add several hundred GB of storage (or better yet, fast storage) to handle PCAP and series of logs.
Useful shortcuts: cheat sheet
Another handy resource is the official log sheet template. This cheat sheet condenses maintenance commands and key file paths , perfect for locating service logs when time is short.
News and constant evolution
The project is moving quickly because the competition is too. One of the major recent updates is version 2.4.120 (February 2025) , which came packed with improvements.
- New alerts interface with AI-powered summaries to understand events at a glance and speed up response.
- Zeek 7 integrated, with expanded support for protocols such as QUIC, HTTP/2, OpenVPN or IPsec, improving detection and analysis.
- ATT&CK Navigator built-in to map events to the MITRE ATT&CK framework and prioritize threats judiciously.
- External API in Security Onion Pro, useful for custom integrations or custom interfaces.
- Local IP address lookup with custom descriptions visible in SOC, very practical if PTRs are missing or critical IPs are to be noted.
In addition to 2.4.120, the release cadence has continued with 2.4.130, 2.4.140, 2.4.141, 2.4.150, 2.4.160 and 2.4.170 throughout 2025, reinforcing that the improvement cycle is continuous and that it is worthwhile to keep up to date.
Common use cases
Security Onion fits into multiple scenarios. From detecting phishing attempts to hunting C2 threats, investigating exfiltrations, or centralizing logs for unified visibility. Its open and modular nature helps adapt it to both small and medium-sized businesses and large data centers.
When to perform network audits with Security Onion?
Regular audits are a fundamental part of any security program. You don't have to wait for a breach to review your network , but there are situations where prioritizing them is essential.
- Changes in infrastructure: new systems, apps, or IT solutions; confirm that everything works together well and without new gaps.
- Security incidents: After a successful attack, auditing is vital to understand the vector and reinforce where necessary.
- Performance issues: Slowness or disconnections can hide failures or abuses that an audit reveals.
- Business expansion: more locations, departments, or staff alter patterns; recalibration is necessary.
- Scheduled evaluations: : for no apparent reason, scheduling regular check-ups helps you get ahead of scares.
In any case, if you lack experience, it is wise to rely on specialized companies that adapt the tests to the environment and avoid hidden costs resulting from poor execution.
Deployment and configuration
Deployment goes beyond simply installing and using the system. It requires defining network interfaces, sensors, alert management, and rules to tailor it to the organization's specific needs. The community and official documentation provide templates and architectural recommendations to help you get started on the right foot.
Practical demonstration: exfiltration investigation
To understand the workflow, we propose a practical exercise: analyze a data exfiltration case using Security Onion tools.
Import PCAP and prepare the environment
Before loading the PCAP, it's a good idea to clean up alerts and visualizations in Elasticsearch with a couple of maintenance commands. After that, import the .pcap file using the appropriate utility.
If something doesn't start on the first try, try restarting your machine. Security Onion orchestrates its services in Docker containers , and it may take a little while to get everything up and running after startup. You can view the real-time status of the containers using the `list` command.
Don't worry if the last three containers appear as DISABLED : that just indicates that there is no real-time capture; the PCAP will still be analyzed with Suricata and Zeek.
Malicious Traffic: Exploring Flows with Security Onion
First TCP flow
- Sort alerts chronologically from that time thread, from least recent to most recent, to see the complete sequence.
- Identify Source IP, destination IP and ports involved in this first exchange towards the Internet.
- Note a curious alert: a PDF is requested directly from an IP instead of a domain; what signature causes it?
- Before that request, appears a user-agent that identifies itself as curl; take note for later correlations.
- The latest flow alert, what does it indicate has happened? Describes the condition that triggers the event.
- Open any of those alerts and load the full stream to review all messages in detail.
- Within that reconstruction, what User Agent exactly you see?
- Do you detect something suspicious in the body of the HTTP response?
- Send this traffic to a kitchen environment like CyberChef to play with him.
- There, go removing layers and transformations until revealing interesting content.
- When reaching the core, do they appear anomalous references or indicators worthy of IOC?
Second TCP flow
- With the ports and IP pairs As a guide, identify which alerts belong to this second flow.
- repeat the traffic reconstruction just like before to see context and payloads.
- Do you find Something out of the ordinary in transactions?
Third TCP flow
- Locate the two alerts that define the flow and notes key parameters (IPs, ports, protocol).
- reopen the packet thread for detailed inspection.
- What User Agent is used and what action is the request trying to perform?
- After this exchange another appears HTTPS traffic alert; according to what we have seen, what would it correspond to?
Fourth TCP stream
- Suddenly they shoot up many different alerts; by your pattern, what seems to have happened?
- How does you go deeper from the alerts to see exactly what happened?
- In the flow view, what key clues are they appreciated?
- open the tab Hunt.
- Throw a predefined query that sorts by event.module and event.dataset.
- In Group Metrics, check what types of logs Zeek has collected.
- In the queries dropdown, choose show all connections by source IP, destination IP, network protocol and destination port.
- Now group by HTTP connections and destination port.
- Does any appear unusual port for HTTP?
- If yes, mark it as Include to focus on him.
- In Events, do you see something worth analyzingOpen it in detail as you already know.
- What find arises there?
Other detection routes
- Group by HTTP connections, method and user-agent.
- What an interesting pattern would allow the identification of malicious traffic by user-agent?
- Group by HTTP virtual host.
- Any virtual host unusual or suspicious that points to malicious activity?
- Group by dataset notice (Zeek).
- What suspicious signal stands out?
- In Events, group by field notice.sub_message.
- What entity are most of them from? TLS certificatesWhat do you deduce?
Security Onion Support, Community, and License
The Security Onion community is very active: forums, groups, and updated documentation help answer questions and share best practices. For organizations that require more, there is commercial support and a Pro edition with additional integration features.
Regarding licensing, the project is free and open-source software . Details and nuances of the license can be found on the official website and repositories.
Privacy and external resources
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If you'd like to learn more or explore business options, please visit our official website: securityonionsolutions.com . For any questions or suggestions, please don't hesitate to contact us , and we'll help guide the implementation process in your specific context.
Security Onion consolidates network capture, host detection, and analytics—essential for a modern SOC—into a single stack. With Suricata, Snort, Zeek, Wazuh, Elastic, Sguil, Squert, CapMe, and CyberChef, visibility expands both in breadth and depth. Add to that comprehensive documentation, virtualization options, a helpful cheat sheet, and a robust release schedule featuring enhancements like the new alerts interface, Zeek 7, and ATT&CK Navigator, and you have a solid foundation for threat hunting and incident response for businesses of all sizes.
