Identify the log sources you want to monitor. Create a Splunk search query that checks for events from those sources within a specific timeframe.
Step 2: Create an Alert
In Splunk, go to Settings > Searches, reports, and alerts. Configure a new alert with the search query from step 1 and set it to run on a schedule. Trigger the alert when the number of results (sources with zero logs) is greater than 0.