CMMC Practice SC.3.191: Protect the confidentiality of CUI at rest.
CMMC CLARIFICATION (Ref CMMC – Appendix B)
CUI at rest means information that does not move through the network and may be stored on hard drives, media, and mobile devices. Develop a scheme and implement the necessary security controls to protect the confidentiality of CUI at rest. Although an approved encryption method protects data stored at rest, there are other additional technical solutions. The scheme you choose should depend on your organization’s environment and business needs.