Customers can now use custom backups, to back up their web app's files and configuration data to a firewall-protected storage account if the following requirements are fulfilled:
- The app is integrated with a virtual network, or the app is in a v3 App Service environment.
- The storage account has granted access from the virtual network that the app is integrated with, or that the v3 App Service environment is created with.
For more information please refer to back-up-and-restore-over-azure-virtual-network