Preventing unauthorized persons from accessing data outside the control of the SQL Server engine is as essential an element of information security as is protecting data while it is under the control of the SQL engine. Such data protection generally focuses on two areas, data at rest and data in transit. Data at rest refers to when data is written to a persisted data store. That includes backups and temporary “scratch” writes such as tempdb. Data in transit, sometimes called data in motion, refers to data communications between the SQL service and a client application, including communication to other SQL Servers and to administrative tools like SSMS or ADS.