Suricata is a free and open source, mature, fast and robust network threat detection engine. Suricata inspects the network traffic using a powerful and extensive rules and signature language, and has powerful Lua scripting support for detection of complex threats.

Suricata NIDS alerts can be found in Alerts, Dashboards, Hunt, and Kibana. Here’s an example of Suricata NIDS alerts in Alerts:


If enabled, Suricata metadata (protocol logs) can be found in Dashboards, Hunt, and Kibana.

Community ID

Security Onion enables Suricata’s built-in support for Community ID.


You can configure Suricata by going to Administration –> Configuration –> suricata.


If you would like to configure/manage IDS rules, please see the Managing Rules and Managing Alerts sections.


The HOME_NET variable defines the networks that are considered home networks (those networks that you are monitoring and defending). The default value is RFC1918 private address space (,, and You can modify this default value by going to Administration –> Configuration –> suricata –> config –> vars –> address-groups –> HOME_NET.


By default, EXTERNAL_NET is set to any (which includes HOME_NET) to detect lateral movement inside your environment. You can modify this default value by going to Administration –> Configuration –> suricata –> config –> vars –> address-groups –> EXTERNAL_NET.


If Suricata is experiencing packet loss, then you may need to do one or more of the following: tune the ruleset (see the Managing Alerts section), apply a BPF, adjust max-pending-packets in the Suricata configuration, or adjust AF-PACKET workers in Administration –> Configuration –> suricata –> config –> af-packet –> threads.

If you have multiple physical CPUs, you’ll most likely want to pin sniffing processes to a CPU in the same Non-Uniform Memory Access (NUMA) domain that your sniffing NIC is bound to. Accessing a CPU in the same NUMA domain is faster than across a NUMA domain.


For more information about determining NUMA domains using lscpu and lstopo, please see:


To edit the thresholding configuration, please see the Managing Alerts section.


Depending on what options you choose in Setup, it may ask if you want to use Zeek or Suricata for metadata. If you choose Suricata, then here are some of the kinds of metadata you can expect to see in Dashboards or Hunt:

  • Connections
  • DHCP
  • DNS
  • Files
  • FTP
  • HTTP
  • SSL

If you later find that some of that metadata is unnecessary, you can filter out the unnecessary metadata by writing rules. We have included some examples at

The global pillar on your manager node controls the metadata engine on each sensor. Only one metadata engine at a time is supported.

To change your grid’s metadata engine from Zeek to Suricata:

  • On the manager, go to Administration –> Configuration –> global –> mdengine and change the value from ZEEK to SURICATA.

  • Stop Zeek on all nodes:

    sudo salt '*' 'so-zeek-stop'
  • Update all nodes:

    sudo salt '*' state.highstate
  • You may need to remove so-zeek from /opt/so/conf/so-status/so-status.conf on each sensor node.

File Extraction

If you choose Suricata for metadata, it will extract files from network traffic and Strelka will then analyze those extracted files. If you would like to extract additional file types, then you can add file types as shown at


Suricata can be disabled by going to Administration –> Configuration –> suricata –> enabled.

Diagnostic Logging

If you need to troubleshoot Suricata, check /opt/so/log/suricata/suricata.log. Depending on what you’re looking for, you may also need to look at the Docker logs for the container:

sudo docker logs so-suricata

Troubleshooting Alerts

If you’re not seeing the Suricata alerts that you expect to see, here are some things that you can check:

  • If you have metadata enabled, check to see if you have metadata for the connections. Depending on your configuration, this could be Suricata metadata or Zeek metadata.
  • If you have metadata enabled but aren’t seeing any metadata, then something may be preventing the process from seeing the traffic. Check to see if you have any BPF configuration that may cause the process to ignore the traffic. If you’re sniffing traffic from the network, verify that the traffic is reaching the NIC using tcpdump. If importing a pcap file, verify that file contains the traffic you expect and that the Suricata process can read the file and any parent directories.
  • Check your HOME_NET configuration to make sure it includes the networks that you’re watching traffic for.
  • Check to see if you have a full NIDS ruleset with rules that should specifically alert on the traffic and that those rules are enabled.
  • Check to see if you have any threshold or suppression configuration that might be preventing alerts.
  • Check the Suricata log for additional clues.
  • Check the Elastic Agent, Logstash, and Elasticsearch logs for any pipeline issues that may be preventing the alerts from being written to Elasticsearch.
  • Try installing a simple import node (perhaps in a VM) following the steps in the First Time Users section and see if you get alerts there. If so, compare the working system to the non-working system and determine where the differences are.


For detailed Suricata statistics, check /opt/so/log/suricata/stats.log.

Testing Rules

To test a new rule, use the following utility on a node that runs Suricata (ie Forward or Import).

sudo so-suricata-testrule <Filename> /path/to/pcap/test.pcap

The file should contain the new rule that you would like to test. The pcap should contain network data that will trigger the rule.


If your network traffic has VLAN tags, then Suricata will log them. Dashboards has a VLAN dashboard which will show this data.

More Information


For more information about Suricata, please see