SC.L2-3.13.16 – DATA AT REST

DISCUSSION [NIST SP 800-171 R2]

Information at rest refers to the state of information when it is not in process or in transit and is located on storage devices as specific components of systems. The focus of protection at rest is not on the type of storage device or the frequency of access but rather the state of the information. Organizations can use different mechanisms to achieve confidentiality protections, including the use of cryptographic mechanisms and file share scanning. Organizations may also use other controls including secure off-line storage in lieu of online storage when adequate protection of information at rest cannot otherwise be achieved or continuous monitoring to identify malicious code at rest.

FURTHER DISCUSSION

CUI at rest means information that is not moving through the network; typically this means data currently stored on hard drives, media, and mobile devices. 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 technical and physical solutions. The methods chosen should depend on the environment and business needs.

Implementing encryption for CUI is one approach to this practice, but it is not mandatory. Physical security is often employed to restrict access to CUI, particularly when it resides on servers within a company’s offices. Other approaches for protecting CUI include system related protections such as configurations and rule sets for firewalls, gateways, intrusion detection/prevention systems, filtering routers, and authenticator content that eliminate attempts at exfiltration. You may also employ other security requirements including secure
off-line storage.

This practice, SC.L2-3.13.16, requires confidentially be provided for CUI at rest and complements MP.L2-3.8.9, which requires confidentially of CUI at backup storage locations. This practice, SC.L2-3.13.16, also leverages SC.L2-3.13.11, which specifies that the algorithms used must be FIPS-validated.

Example 1

Your company has a policy stating CUI must be protected at rest and you work to enforce that policy. You research Full Disk Encryption (FDE) products that meet the FIPS encryption requirement. After testing, you deploy the encryption to all computers to protect CUI at rest [a].

Example 2

You have used encryption to protect the CUI on most of the computers at your company, but you have some devices that do not support encryption. You create a policy requiring these devices to be signed out when needed, stay in possession of the signer when checked out, and to be signed back in and locked up in a secured closet when the user is done with the device [a]. At the end of the day each Friday, you audit the sign-out sheet and make sure all devices are returned to the closet.

Potential Considerations

Is the confidentiality of CUI at rest protected using encryption of storage devices and/or appropriate physical methods [a]?

Copyright

This material is based upon work funded and supported by the Department of Defense under Contract No. FA8702-15-D-0002 with Carnegie Mellon University for the operation of the Software Engineering Institute, a federally funded research and development center, and under Contract No. HQ0034-13-D-0003 and Contract No. N00024-13-D-6400 with the Johns Hopkins University Applied Physics Laboratory LLC, a University Affiliated Research Center.

The view, opinions, and/or findings contained in this material are those of the author(s) and should not be construed as an official Government position, policy, or decision, unless designated by other documentation.

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