Suricata

From https://suricata-ids.org:

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:

_images/alerts.png

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

Community ID

Security Onion enables Suricata’s native support for Community ID.

Performance

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.

To change the number of workers:

  • Stop sensor processes:

    sudo so-suricata-stop
    
  • Edit /opt/so/saltstack/local/pillar/minions/$SENSORNAME_$ROLE.sls and change the suriprocs variable to the desired number of workers.

  • Start sensor processes:

    sudo so-suricata-start
    

See also

For best performance, Suricata should be pinned to specific CPUs. In most cases, you’ll 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.

See also

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

To pin Suricata workers to specific CPUs:

  • Stop sensor processes:

    sudo so-suricata-stop
    
  • Edit /opt/so/saltstack/local/pillar/minions/$SENSORNAME_$ROLE.sls and add the following under sensor:

    suripins:
      - <cpu_1>
      - <cpu_2>
      - <cpu_3>
    
  • Note: To avoid inconsistent Suricata workers being allocated, ensure suriprocs is removed from under sensor: or is equivalent to the number of cpu cores being pinned.

  • Start sensor processes:

    sudo so-suricata-start
    

HOME_NET

To configure HOME_NET, please see the Homenet section.

Configuration

You can configure Suricata’s suricata.yaml using Salt. The defaults for this have been defined in https://github.com/Security-Onion-Solutions/securityonion/blob/master/salt/suricata/defaults.yaml. Under suricata:config, the pillar structure follows the same YAML structure of the suricata.yaml file.

For example, suppose you want to change Suricata’s EXTERNAL_NET setting from the default of any to !$HOME_NET. You could add the following to the global pillar file (/opt/so/saltstack/local/pillar/global.sls) or minion pillar file (/opt/so/saltstack/local/pillar/minions/$SENSORNAME_$ROLE.sls) on the manager:

suricata:
  config:
    vars:
      address-groups:
        EXTERNAL_NET: "!$HOME_NET"

From the manager, then run:

sudo salt $SENSORNAME_$ROLE state.highstate

Some of the settings normally found in suricata.yaml can be found in the sensor pillar instead of the Suricata pillar. These options are: HOMENET, default-packet-size, and the CPU affinity settings for pinning the processes to CPU cores or how many processes to run.

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

Thresholding

To enable thresholding for SIDS, reference the example pillar at https://github.com/Security-Onion-Solutions/securityonion/blob/master/pillar/thresholding/pillar.example.

To view the acceptable syntax, view the file located at https://github.com/Security-Onion-Solutions/securityonion/blob/master/pillar/thresholding/pillar.usage.

This pillar can be added to Salt in either the global pillar file (/opt/so/saltstack/local/pillar/global.sls) or minion pillar file (/opt/so/saltstack/local/pillar/minions/$SENSORNAME_$ROLE.sls).

Warning

Salt sls files are in YAML format. When editing these files, please be very careful to respect YAML syntax, especially whitespace. For more information, please see https://docs.saltproject.io/en/latest/topics/troubleshooting/yaml_idiosyncrasies.html.

Metadata

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 and later find that some metadata is unnecessary, you can filter out the unnecessary metadata by writing rules. We have included some examples at https://github.com/Security-Onion-Solutions/securityonion/blob/dev/salt/idstools/sorules/filters.rules.

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, edit the global pillar file (/opt/so/saltstack/local/pillar/global.sls) and change the mdengine variable from ZEEK to SURICATA.

  • Stop Zeek on all nodes:

    sudo salt '*' cmd.run '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 https://github.com/Security-Onion-Solutions/securityonion/blob/dev/salt/idstools/sorules/extraction.rules.

Disabling

Suricata can be disabled by setting enabled: false in the suricata Salt pillar.

If you just want to disable Suricata on a single sensor, then you can edit that sensor’s minion.sls file. If the file doesn’t already have a suricata section, then add the following to the end of the file:

suricata:
  enabled: false

If you want to disable Suricata globally across all your sensors, then you could add that entry to your global.sls file.

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 Homenet 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 Filebeat, Logstash, and Elasticsearch logs for any pipeline issues that may be preventing the alerts from being written to the so-ids indices.
  • 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.

Stats

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.

More Information

See also

For more information about Suricata, please see https://suricata-ids.org.