Microsoft Information Protection

Check out my earlier Post on AIP (feb 2019)

End-to-end life-cycle for encrypting files using Azure Information Protection (AIP)

Use "Unified Labeling" to create labels

Note: Encrypting stops SharePoint being able to look into the content of the file.  The labels and name are still search but not the content of the file.  eDiscovery, Search, co-authoring don't work on AIP encrypted documents.

Cloud App Security (MCAS) Screen Shot