Information
Ensure user databases are encrypted using Transparent Data Encryption (TDE). Backups of databases encrypted with TDE are automatically encrypted as well.
A malicious party who steals physical media like drives or backup tapes can restore or attach the database and browse its data.
One solution is to encrypt sensitive data in a database and use a certificate to protect the keys that encrypt the data. This solution prevents anyone without the keys from using the data.
Solution
Implement TDE encryption on each user database with sensitive data.
More info on how to do this is available here:
https://learn.microsoft.com/en-us/sql/relational-databases/security/encryption/transparent-data-encryption
Impact:
A database datafile, logfile or backup accidentally exposed to the Internet or transmitted outside a secure environment can be easily copied/restored to a SQL Server anywhere and its contents discovered.