The Loopback Service driver is shipped with packages. You can create the driver in Designer. If your requirements for the driver are different from the default policies, you need to modify the default policies to do what you want.
Data flow between the Loopback Service driver and the Identity Vault is controlled by the filters, mappings, and policies that are in place for the Loopback Service driver.
The driver filter determines which classes and attributes are synchronized between the driver and the Identity Vault, and in which direction synchronization takes place.