Connect Syslog Data Sources to Azure Sentinel

By Ashwin Venugopal -

 



Plan for the Syslog Connector

The events from Linux-based, Syslog-supporting machines or appliances can be streamed into Azure Sentinel using the Log Analytics agent for Linux. The host's native Syslog daemon will collect local events of the specified types and forward them locally to the agent, which will stream them to your Log Analytics workspace.

Log Analytics also helps in collecting the messages sent by the rsyslog or syslog-ng daemons, where rsyslog is the default that's on version 5 of Red Hat Enterprise Linux (RHEL), CentOS, and Oracle except for the Linux version sysklog Syslog event collection and the rsyslog daemon should be installed and configured to replace sysklog for these versions of Linux.

How it works?

Syslog is an event logging protocol that is common to Linux and when the Log Analytics agent for Linux is installed on your VM or appliance, the installation routine configures the local Syslog daemon to forward messages to the agent on TCP port 25224 which in turn sends the message to your Log Analytics workspace over HTTPS, where it can be parsed into an event log entry in the Syslog table in the Azure Sentinel Logs.  

Collect data from Linux-based sources using Syslog

To view the connector page:
  1. Select Data connector page.
  2. Select Syslog.
  3. Then select the Open connector page on the preview pane.
  4. Verify that you have the appropriate permissions.
  5. Select the Choose where to install the agent option to expand the instructions.  

For an Azure Linux VM:

To install the agent on an Azure Linux VM:
  1. Install agent on Azure Linux Virtual Machine.
  2. Select the link Download and install agent for Azure Linux VMs.
  3. Select Connect on teh row of the Linux VM. 

For any other Linux machine:

To install the agent on non-Azure Linux virtual hosts:
  1. Install agent on non-Azure Linux Machine.
  2. Select the link Download and install agent for non-Azure Linux machines.
  3. In the Agents management blade, select the Linux servers tab.
  4. Copy the command for Download and onboard agent for Linux and run it on your Linux machine.
  5. The page also displays your Workspace ID, primary key, and secondary key.  

Configure the log analytics agent

The Log Analytics Agent for Linux can only collect events with the facilities and severities that are specified in its configuration and to configure the Log Analytics agent for syslog facilities you should:
  • Access the Log Analytics Workspace Advanced Settings page- 

  1. From the Syslog Data connector page, select Open your Workspace advanced settings configuration.
  2. From the Azure Sentinel portal, select Settings in the Configuration area. Select Workspace Settings Tab. Select Advanced settings in the Settings area.        

  • Select Data.
  • Select Syslog.
  • Select the option Apply below configuration to my machines
  • Enter the facility name and select + for each facility. 

If you want to configure Syslog manually on each Linux agent, then uncheck the box Apply below configuration to my machines. The following facilities are supported with the Syslog collector:

  • kern
  • user
  • mail
  • daemon
  • auth
  • syslog
  • lpr
  • news
  • uucp
  • cron
  • authpriv
  • ftp
  • local0-local7

Parse syslog data with KQL

The Syslog collector writes log data to the Syslog table whereas the CEF Connector writes to the CommonSecurityLog with the fields already parsed. A parser is known as a KQL Function that is a query saved as a function and then referenced with the function name which is like accessing any other table. After creating the parses, you only need to write the SyslogMessage parsing once. 

In the Logs window, create query, select the Save button, and select Function from the drop-down, after that specify function name and alias. For example, if we create the Function named MyParser, we then can access the table using the name MyParser.










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