Collect data from Splunk via Syslog

See the changelog of the Syslog Listener type here.

Splunk Setup

The usual scenario for adapting Splunk data for sending via the Syslog Listener involves using a Splunk Heavy Forwarder (HF), configuring three specific configuration files: outputs.conf, props.conf, and transforms.conf.

The HF is necessary because Universal Forwarders (UFs) lack the processing capabilities to format and route data to a third-party system using the Syslog protocol.

See here for more information on types of Splunk forwarders.

You will need to create or edit these files, typically located in $SPLUNK_HOME/etc/system/local/ or a custom app directory on your Heavy Forwarder.

1. Define the Syslog Destination

The outputs.conf file tells the Heavy Forwarder where to send the data. You must define a Syslog output group ([syslog:<target_group>]) rather than a standard TCP output group.

Configuration	Example Value	Description
Syslog Group	[syslog]	Defines the default syslog output settings.
Default Group	defaultGroup = onum_syslog_group	Specifies the default target group for all unrouted data. If you only want to send a subset of logs, do not set a defaultGroup here.
Target Stanza	[syslog:onum_syslog_group]	Defines the specific ONUM destination.
Server	server = 10.1.1.200:514	server = [<onum_siem_ip>|<onum_siem_host>]:<port> The IP address and port (default is UDP 514) of the ONUM Syslog receiver.
Data Format	sendCookedData = false	CRITICAL. This ensures Splunk sends the raw, unprocessed log data (not Splunk's internal 'cooked' format).
Protocol	type = udp (or tcp)	Specifies the transport protocol. Syslog traditionally uses UDP, but TCP is often preferred for reliability.

# $SPLUNK_HOME/etc/system/local/outputs.conf

[syslog]
defaultGroup = onum_syslog_group 

[syslog:onum_syslog_group]
server = 10.1.1.200:514
sendCookedData = false
type = udp

2. Selective Routing (Recommended)

To avoid sending all data from the Heavy Forwarder to Onum, you typically use props.conf and transforms.conf to filter and route only the desired events (e.g., logs from a specific sourcetype or index).

Please note that the form may look different if you are using this Listener in a cloud environment. For more information on this, see the main article on Collecting data using Syslog. The steps will be the same, just make sure to enter the Onum URL in the Splunk configuration.

Onum Setup

1

Log in to your Onum tenant and click Listeners > New listener.

2

Double-click the Syslog Listener.

3

Enter a Name for the new Listener. Optionally, add a Description and some Tags to identify the Listener.

4

Enter the required Port and Protocol (TCP or UDP). For cloud-based Onum installations, the Socket and Protocol sections are not visible (port 443 and Protocol TCP are used by default). If you see it, enter the required port in the Port field.

Note that by default, available TCP ports are 1024 to 10000.

While UDP 514 is the standard, some implementations may use TCP 514 or other ports, depending on specific configurations or security requirements. To determine the syslog port value, check the configuration settings of your syslog server or consult the documentation for your specific device or application.

5

Choose the required Framing Method, which refers to how characters are handled in log messages sent via the Syslog protocol. Choose between:

• Auto-Detect - automatically detect the framing method using the information provided.

• Non-Transparent Framing (newline) - the newline characters (\n) within a log message are preserved as part of the message content and are not treated as delimiters or boundaries between separate messages.

• Non-Transparent Framing (zero) - refers to the way zero-byte characters are handled. Any null byte (\0) characters that appear within the message body are preserved as part of the message and are not treated as delimiters or boundaries between separate messages.

• Non-Transparent Framing (custom) - choose this option if you need to use vendor-specific or custom approaches to frame syslog messages rather than the standard framing methods. You must enter the specific character(s) that will mark the end of each syslog message in the Custom trailer characters parameter that appears.

• Octet Counting (message length) - the Syslog message is preceded by a count of the length of the message in octets (bytes).

6

In cloud-based Onum installations, the TLS configuration section is not visible. In these setups, Onum automatically manages TLS certificates, eliminating the need for manual configuration.

If you see this section, you must enter the required Certificate, Private key and CA Chain. Learn how to generate these self-signed certificates in this article. Once you have them, click New secret in each field and add the corresponding values.

Now there are two possible scenarios:

If you didn't enter your TLS certificates, when you click Create listener you'll see the Network configuration screen, which shows the Address and Port needed to communicate with Onum. Here you will download the certificate (see the steps after creation to do this).

You can access all this information in the Listener details after creation, so don't worry.

If you entered the TLS certificates, you'll go directly to the Labels when you eventually click create Listener.

7

The TLS credentials are saved in Onum as Secrets. In the TLS form, click New secret to create a new one:

• Give the secret a Name.

• Turn off the Expiration date option.

• Click Add new value.

• Click Save.

Learn more about secrets in Onum in this article.

You can now select the secret you just created in the corresponding fields.

8

Finally, click Create labels. Optionally, you can set labels to be used for internal Onum routing of data. By default, data will be set as Unlabeled.

Learn more about labels in this article.

Click Create listener when you're done.