ATP is Azure Threat Protection cloud service that helps protect your organization from insider threats and compromised identities. It constantly monitors the domain controllers and analyzes events. It identifies threat patterns and their source, both on-premises and in the cloud.

In Azure portal you might find costs about ATP. Costs that are calculated by MSFT. They can get generated because of the amount of data ingresses and egresses out of a storage account for malware scanning and reporting.

Azure Defender is a set of security scanning and reporting tools. There are Defender offerings for Compute, Storage, Networking etc. ATP for Storage is part of Defender for Storage offering, it covers Vulnerability scanning and specifically Malware detection for content coming in and out of a storage account.

This is part of Azure Defender for Storage and you can find more about Pricing—Microsoft Defender | Microsoft Azure