Firewall

This section will cover both network firewalls outside of Security Onion and the host-based firewall built into Security Onion.

Network Firewalls

This first sub-section will discuss network firewalls outside of Security Onion.

Internet Communication

When configuring network firewalls for Internet-connected deployments (non-Airgap), you’ll want to ensure that the deployment can connect outbound (TCP/443) to the following:

• raw.githubusercontent.com (Security Onion public key)

• sigs.securityonion.net (Signature files for Security Onion containers)

• ghcr.io (Container downloads)

• pkg-containers.githubusercontent.com (Container downloads)

• rules.emergingthreatspro.com (Emerging Threats IDS rules)

• rules.emergingthreats.net (Emerging Threats IDS open rules)

• github.com (Strelka and Sigma rules updates)

• objects.githubusercontent.com (Strelka and Sigma rules updates)

If you are using our ISO image, you will also need access to the following:

• repo.securityonion.net (primary repo for Oracle Linux package updates)

• repo-alt.securityonion.net (secondary repo for Oracle Linux package updates)

• so-repo-east.s3.us-east-005.backblazeb2.com (secondary repo for Oracle Linux package updates)

If you are not using our ISO image and are instead performing a Network Installation, you will also need access to the following:

• update repo for whatever base OS you’re installing on (OS packages)

• download.docker.com (Docker packages)

• repo.saltstack.com (Salt packages)

If you choose to enable GeoIP updates for Elasticsearch, you will also need access to the following:

• geoip.elastic.co

• storage.googleapis.com

If you choose to enable the Snort Talos ruleset, you will also need access to the following:

• www.snort.org

Node Communication

When configuring network firewalls for distributed deployments, you’ll want to ensure that nodes can connect as shown in the table below. Please note that some of the sources and destinations listed in the table have specific definitions:

• Security Onion grid nodes includes any node joined to your manager. This includes search nodes, sensors, fleet nodes, receiver nodes, and IDH nodes.

• Search nodes are grid nodes that run Elasticsearch and join to the manager to enlarge its Elastic cluster.

• Elastic cluster nodes include the search nodes and the manager itself.

• Endpoint Elastic Agents includes any endpoint where you have deployed the Elastic Agent and want to send the data to your Security Onion grid.

Source (SRC)	Destination (DST)	Destination Port(s) (TCP)	Description
Security Onion grid nodes	Manager	443, 4505, 4506, 5000, 5055, 8086, 8220, 8443	Management, Registry, Salt, Updates
Security Onion grid nodes	Fleet node	5055, 8220	Elastic Agent data and management
Security Onion grid nodes	Receiver node	5055	Elastic Agent data
Search nodes	Manager	443, 4505, 4506, 5000, 5055, 8086, 8220, 8443, 9696	Management, Registry, Salt, Updates, Redis
Elastic cluster nodes	Elastic cluster nodes	9200, 9300	Logstash to Elasticsearch and Elasticsearch node-to-node
Endpoint Elastic Agents	Manager	8220, 8443, 5055	Elastic Agent management, binary updates, data
Endpoint Elastic Agents	Fleet node	5055, 8220	Elastic Agent management and data
Endpoint Elastic Agents	Receiver node	5055	Elastic Agent data
Fleet node	Receiver node	5056	Logstash-to-Logstash
Fleet node	Manager	5056, 9200	Logstash-to-Logstash and Elasticsearch node-to-node
Manager	IDH node	2222	SSH for management

Host Firewall

The remainder of this section will cover the host firewall built into Security Onion.

Note

Security Onion locks down the firewall by default.

Configuring Host Firewall

You can configure the firewall by going to Administration –> Configuration –> firewall –> hostgroups.

If for some reason you can’t access Security Onion Console (SOC) at all, you can use the so-firewall command to allow the IP address of your web browser to connect (replacing <IP ADDRESS> with the actual IP address of your web browser):

sudo so-firewall includehost analyst <IP ADDRESS>

Reviewing Host Firewall

You can view the entire firewall configuration from the command line using the iptables command like this:

sudo iptables -nvL

Warning

You can use this command to view the iptables configuration, but please do not modify the firewall manually using iptables as it is managed by Salt. You should only make changes via the Configuration screen as shown above.

Port Groups

Port groups are a way of grouping together ports similar to a firewall port/service alias. For example, if you have a web server you might add ports 80 and 443 into a port group.

Host Groups

Host groups are similar to port groups but for storing lists of hosts that will be allowed to connect to the associated port groups.

Function

The firewall state is designed with the idea of creating port groups and host groups, each with their own alias or name, and associating the two in order to create an allow rule. A node that has a port group and host group association assigned to it will allow those hosts to connect to those ports on that node.

The default allow rules for each node are defined by its role (manager, searchnode, sensor, heavynode, etc) in the grid. Host groups and port groups can be created or modified from the manager node by going to Administration –> Configuration –> firewall –> hostgroups. When setup is run on a new node, it will ask the manager to add itself to the appropriate host groups. All node types are added to the minion host group to allow Salt communication. If you were to add a search node, you would see its IP appear in both the minion and the search_node host groups.

Advanced Firewall Config

When you go to Administration –> Configuration –> firewall, you will only see hostgroups by default. If you need to modify port groups, then you will need to click the Options menu and then enable the Show advanced settings option.

Modifying a default port group

The analyst hostgroup is allowed access to the nginx ports which are 80 and 443 by default. In this example, we will extend the default nginx port group to include a custom port.

1. At the top of the page, click the Options menu and then enable the Show advanced settings option.

2. On the left side, go to firewall, select portgroups, locate the nginx portgroup, and then select tcp.

3. On the right side, select the manager node, specify your custom port to be added, and then click the checkmark to save the value.

4. If you would like to apply the rules immediately, click the SYNCHRONIZE GRID button under the Options menu at the top of the page.

Creating a custom host group with a custom port group

In this example, we will add a new custom hostgroup to allow a custom set of hosts to connect to a custom port on an IDH node.

1. At the top of the page, click the Options menu and then enable the Show advanced settings option.

2. On the left side, go to firewall, select hostgroups, and then select customhostgroup0.

3. On the right side, select the IDH node that you want to allow access to, add the list of hosts that require access, and then click the checkmark to save the value.

4. On the left side, go to firewall, select portgroups, select customportgroup0, and then select the appropriate protocol.

5. On the right side, select the IDH node that you want to allow access to, add your custom port, and then click the checkmark to save the value.

6. On the left side, go to firewall, role, and then select idh, chain, DOCKER-USER, hostgroups, customhostgroup0, portgroups.

7. On the right side, select the IDH node that you want to allow access to, add the portgroup customportgroup0, and then click the checkmark to save the value.

8. The next time the IDH node checks in, it should get the appropriate firewall rules.