Public IP alert can be created through Azure Activity Logs. You'll have to enable the Azure activity logs collections and then need to write a custom query alert on the Applogs page. To enable the azure activity logs, go to Admin --> Applogs --> Settings --> Enable azure logs.
Step 1: Go to app logs page
Step 2: Run following query logtype="Azure Logs" and operationname CONTAINS "Create or Update Public Ip Address"
Step 3: Select the Alerts Option
Step 4: Fill the Threshold profile and log check frequency and save the alerts. This custom monitor will trigger the alert whenever any new public IP is created on the subscriptions.
-- Site24x7 Team