Details on pre-requisites, configuring the add-on and viewing the data in Azure Sentinel is covered in this section.

Background

When you add data to Splunk, the Splunk indexer processes it and stores it in a designated index (either, by default, in the main index or in the one that you identify). Searching in Splunk involves using the indexed data for the purpose of creating metrics, dashboards and alerts. This Splunk add-on triggers an action based on the alert in Splunk. You can use Alert actions to define third-party integrations (like Microsoft Sentinel Log Analytics).

This add-on uses the Azure Log Analytics Data Collector API to send log data to Microsoft Sentinel. All data in the Log Analytics workspace is stored as a record with a particular record type. You can format your data to send to the HTTP Data Collector API as multiple records in JSON. When you submit the data, an individual record is created in the repository for each record in the request payload.

Pre-requisites

• Onboard Splunk instance(latest release)
• Get the Log Analytics workspace parameters: Workspace ID and Primary Key from here

• Install the Microsoft Sentinel Add-on for Splunk

  • In Splunk home screen, on the left side sidebar, click "+ Find More Apps" in the apps list, or click the gear icon next to Apps then select Browse more apps.

  

  • Search for Microsoft Sentinel in the text box, find the Microsoft Sentinel Add-On for Splunk and click Install.
  • After the add-on is installed reboot of Splunk is required, click Restart Now.

Configure the Microsoft Sentinel add-on for Splunk

Refer to Define RealTime Alerts documentation to set up Splunk alerts to send logs to Microsoft Sentinel. To validate the integration, the audit index is used as an example, for an “_audit”- this repository stores events from the file system change monitor, auditing, and all user search history. You can query the data by using index=”_audit” in the search field as illustrated below.

Then use a scheduled or real-time alert to monitor events or event patterns as they happen. You can create real-time alerts with per-result triggering or rolling time window triggering. Real-time alerts can be costly in terms of computing resources, so consider using a scheduled alert, when possible.

Set up alert actions, which can help you respond to triggered alerts. You can enable one or more alert actions. Select “Send to Microsoft Sentinel” action, which appears after you install the Microsoft-Sentinel add-on as shown in the diagram below.

Fill in the required parameters as shown in the diagram below:

• Customer_id: Microsoft Sentinel Log Analytics Workspace ID
• Shared_key: Microsoft Sentinel Log Analytics Primary Key
• Log_Type: Microsoft Sentinel custom log name

Note: These parameters are required and will be used by the application to send data to Microsoft Sentinel through the HTTP Data Collector API.

View Splunk Data in Microsoft Sentinel
The logs will go to a custom Microsoft Sentinel table called ‘Splunk_Audit_Events_CL’ as shown below. The table name aligns with the log name provided in the Figure 4 above. It can take few minutes for events to be available.

You can query the data in Microsoft Sentinel using Kusto Query Language (KQL) as shown below.

Splunk_Audit_Events_CL 
 | summarize count() by user_s, action_s
 | render barchart 

When a correlation search included in the Splunk Enterprise Security or added by a user, identifies an event or pattern of events, it creates an incident called notable event. Correlation searches filter the IT security data and correlate across events to identify a particular type of incident (or pattern of events) and then create notable events.
Correlation searches run at regular intervals (for example, every hour) or continuously in real-time and search events for a particular pattern or type of activity. The notable event is stored in a dedicated notable index. You can import all notable events into Azure Sentinel using the same procedure described above.

The results will be added to a custom Microsoft Sentinel table called ‘Splunk_Notable_Events_CL’ as shown below.