The protection of Controlled Unclassified Information $($CUI$)$ resident in nonfederal systems and organizations is of paramount importance to federal agencies and can directly impact the ability of the federal government to successfully conduct its assigned missions and business operations. If Sifers$-$Grayson continues to do business with the DoD and DHS$,$ certain modifications to the company's information systems and infrastructures will be required to ensure appropriate processing, storage, and transmission of CUI. Which of the following guidance documents is the best choice for Sifers$-$Grayson to follow when upgrading its infrastructure to comply with federal requirements for safeguarding CUI?

Question $23$ options:

NIST SP $800-128$

NIST SP $800-171$

NIST SP $800-61$

DFARS $252\mathrm{.}239-7009$