NIST SP 800-171 Revision 2



Publication Date:

January 28, 2021

1. Introduction

The Need to Protect Controlled Unclassified Information

Today, more than at any time in history, the federal government is relying on external service providers to help carry out a wide range of federal missions and business functions using information systems. Many federal contractors process, store, and transmit sensitive federal information to support the delivery of essential products and services to federal agencies (e.g., providing financial services; providing web and electronic mail services; processing security clearances or healthcare data; providing cloud services; and developing communications, satellite, and weapons systems). Federal information is frequently provided to or shared with entities such as state and local governments, colleges and universities, and independent research organizations. The protection of sensitive federal information while residing in nonfederal systems and organizations is of paramount importance to federal agencies, and can directly impact the ability of the federal government to carry out its designated missions and business operations.

The protection of unclassified federal information in nonfederal systems and organizations is dependent on the federal government providing a process for identifying the different types of information that are used by federal agencies. EO 13556 established a governmentwide Controlled Unclassified Information (CUI) Program to standardize the way the executive branch handles unclassified information that requires protection. Only information that requires safeguarding or dissemination controls pursuant to federal law, regulation, or governmentwide policy may be designated as CUI. The CUI Program is designed to address several deficiencies in managing and protecting unclassified information to include inconsistent markings, inadequate safeguarding, and needless restrictions, both by standardizing procedures and by providing common definitions through a CUI Registry NARA CUI. The CUI Registry is the online repository for information, guidance, policy, and requirements on handling CUI, including issuances by the CUI Executive Agent. The CUI Registry identifies approved CUI categories, provides general descriptions for each, identifies the basis for controls, and sets out procedures for the use of CUI including, but not limited to, marking, safeguarding, transporting, disseminating, reusing, and disposing of the information.

EO 13556 also required that the CUI Program emphasize openness, transparency, and uniformity of governmentwide practices, and that the implementation of the program take place in a manner consistent with applicable policies established by the Office of Management and Budget (OMB) and federal standards and guidelines issued by the National Institute of Standards and Technology (NIST). The federal CUI regulation,developed by the CUI Executive Agent, provides guidance to federal agencies on the designation, safeguarding, dissemination, marking, decontrolling, and disposition of CUI, establishes self-inspection and oversight requirements, and delineates other facets of the program.

Purpose And Applicability

The purpose of this publication is to provide federal agencies with recommended security requirements for protecting the confidentiality of CUI: (1) when the CUI is resident in a nonfederal system and organization; (2) when the nonfederal organization is not collecting or maintaining information on behalf of a federal agency or using or operating a system on behalf of an agency; and (3) where there are no specific safeguarding requirements for protecting the confidentiality of CUI prescribed by the authorizing law, regulation, or governmentwide policy for the CUI category listed in the CUI Registry.

The requirements apply to components of nonfederal systems that process, store, or transmit CUI, or that provide security protection for such components. If nonfederal organizations designate specific system components for the processing, storage, or transmission of CUI, those organizations may limit the scope of the security requirements by isolating the designated system components in a separate CUI security domain. Isolation can be achieved by applying architectural and design concepts (e.g., implementing subnetworks with firewalls or other boundary protection devices and using information flow control mechanisms). Security domains may employ physical separation, logical separation, or a combination of both. This approach can provide adequate security for the CUI and avoid increasing the organization’s security posture to a level beyond that which it requires for protecting its missions, operations, and assets.

The recommended security requirements in this publication are intended for use by federal agencies in appropriate contractual vehicles or other agreements established between those agencies and nonfederal organizations. In CUI guidance and the CUI Federal Acquisition Regulation (FAR), the CUI Executive Agent will address determining compliance with security requirements.

In accordance with the federal CUI regulation, federal agencies using federal systems to process, store, or transmit CUI, at a minimum, must comply with:

  • Federal Information Processing Standards (FIPS) Publication 199, Standards for Security Categorization of Federal Information and Information Systems (moderate confidentiality);
  • Federal Information Processing Standards (FIPS) Publication 200, Minimum Security Requirements for Federal Information and Information Systems;
  • NIST Special Publication 800-53, Security and Privacy Controls for Federal Information Systems and Organizations; and
  • NIST Special Publication 800-60, Guide for Mapping Types of Information and Information Systems to Security Categories.

The responsibility of federal agencies to protect CUI does not change when such information is shared with nonfederal partners. Therefore, a similar level of protection is needed when CUI is processed, stored, or transmitted by nonfederal organizations using nonfederal systems. The recommended requirements for safeguarding CUI in nonfederal systems and organizations are derived from the above authoritative federal standards and guidelines to maintain a consistent level of protection. However, recognizing that the scope of the safeguarding requirements in the federal CUI regulation is limited to the security objective of confidentiality (i.e., not directly addressing integrity and availability) and that some of the security requirements expressed in the NIST standards and guidelines are uniquely federal, the requirements in this publication have been tailored for nonfederal entities.

The tailoring criteria described in Chapter Two are not intended to reduce or minimize the federal requirements for the safeguarding of CUI as expressed in the federal CUI regulation. Rather, the intent is to express the requirements in a manner that allows for and facilitates the equivalent safeguarding measures within nonfederal systems and organizations and does not diminish the level of protection of CUI required for moderate confidentiality. Additional or differing requirements, other than the requirements described in this publication, may be applied only when such requirements are based on law, regulation, or governmentwide policy and when indicated in the CUI Registry as CUI-specified or when an agreement establishes requirements to protect CUI Basic at higher than moderate confidentiality. The provision of safeguarding requirements for CUI in a specified category will be addressed by the National Archives and Records Administration (NARA) in its CUI guidance and in the CUI FAR; and reflected as specific requirements in contracts or other agreements. Nonfederal organizations may use the same CUI infrastructure for multiple government contracts or agreements, if the CUI infrastructure meets the safeguarding requirements for the organization’s CUI-related contracts and/or agreements including any specific safeguarding required or permitted by the authorizing law, regulation, or governmentwide policy.

Target Audience

This publication serves a diverse group of individuals and organizations in both the public and private sectors including, but not limited to, individuals with:

  • System development life cycle responsibilities (e.g., program managers, mission/business owners, information owners/stewards, system designers and developers, system/security engineers, systems integrators);
  • Acquisition or procurement responsibilities (e.g., contracting officers);
  • System, security, or risk management and oversight responsibilities (e.g., authorizing officials, chief information officers, chief information security officers, system owners, information security managers); and
  • Security assessment and monitoring responsibilities (e.g., auditors, system evaluators, assessors, independent verifiers/validators, analysts).

The above roles and responsibilities can be viewed from two distinct perspectives: the federal perspective as the entity establishing and conveying the security requirements in contractual vehicles or other types of inter-organizational agreements; and the nonfederal perspective as the entity responding to and complying with the security requirements set forth in contracts or agreements.

Organization Of This Special Publication

The remainder of this special publication is organized as follows:

  • Chapter Two describes the fundamental assumptions and methodology used to develop the security requirements for protecting the confidentiality of CUI; the format and structure of the requirements; and the tailoring criteria applied to the NIST standards and guidelines to obtain the requirements.
  • Chapter Three describes the fourteen families of security requirements for protecting the confidentiality of CUI in nonfederal systems and organizations.
  • Supporting appendices provide additional information related to the protection of CUI in nonfederal systems and organizations including: general references; definitions and terms; acronyms; mapping tables relating security requirements to the security controls in SP 800- 53 and ISO 27001; and tailoring actions applied to the moderate security control baseline.

2. The Fundamentals

Assumptions and Methodology for Developing Security Requirements

This chapter describes the assumptions and the methodology used to develop the recommended security requirements to protect CUI in nonfederal systems and organizations; the structure of the basic and derived security requirements; and the tailoring criteria applied to the federal information security requirements and controls.

Basic Assumptions

The recommended security requirements described in this publication have been developed based on three fundamental assumptions:

  • Statutory and regulatory requirements for the protection of CUI are consistent, whether such information resides in federal systems or nonfederal systems including the environments in which those systems operate;
  • Safeguards implemented to protect CUI are consistent in both federal and nonfederal systems and organizations; and
  • The confidentiality impact value for CUI is no less than FIPS 199 moderate.

The assumptions reinforce the concept that federal information designated as CUI has the same intrinsic value and potential adverse impact if compromised—whether such information resides in a federal or a nonfederal organization. Thus, protecting the confidentiality of CUI is critical to the mission and business success of federal agencies and the economic and national security interests of the nation. Additional assumptions also impacting the development of the security requirements and the expectation of federal agencies in working with nonfederal entities include:

  • Nonfederal organizations have information technology infrastructures in place, and are not necessarily developing or acquiring systems specifically for processing, storing, or transmitting CUI;
    • Nonfederal organizations have specific safeguarding measures in place to protect their information which may also be sufficient to satisfy the security requirements;
    • Nonfederal organizations may not have the necessary organizational structure or resources to satisfy every security requirement and may implement alternative, but equally effective, security measures to compensate for the inability to satisfy a requirement; and
    • Nonfederal organizations can implement a variety of potential security solutions directly or using external service providers (e.g., managed services) to satisfy security requirements.

Development Of Security Requirements

The security requirements for protecting the confidentiality of CUI in nonfederal systems and organizations have a well-defined structure that consists of a basic security requirements section and a derived security requirements section. The basic security requirements are obtained from FIPS 200, which provides the high-level and fundamental security requirements for federal information and systems. The derived security requirements, which supplement the basic security requirements, are taken from the security controls in SP 800-53. Starting with the security requirements and the security controls in the moderate baseline (i.e., the minimum level of protection required for CUI in federal systems and organizations), the requirements and controls are tailored to eliminate requirements, controls, or parts of controls that are:

  • Uniquely federal (i.e., primarily the responsibility of the federal government);
  • Not directly related to protecting the confidentiality of CUI; or
  • Expected to be routinely satisfied by nonfederal organizations without specification.

The following Media Protection family example illustrates the structure of a CUI requirement:

Basic Security Requirements

3.8.1 Protect (i.e., physically control and securely store) system media containing CUI, both paper and digital.

3.8.2 Limit access to CUI on system media to authorized users.

3.8.3 Sanitize or destroy system media containing CUI before disposal or release for reuse.

Derived Security Requirements

3.8.4 Mark media with necessary CUI markings and distribution limitations.

3.8.5 Control access to media containing CUI and maintain accountability for media during transport outside of controlled areas.

3.8.6 Implement cryptographic mechanisms to protect the confidentiality of CUI stored on digital media during transport unless otherwise protected by alternative physical safeguards.

3.8.7 Control the use of removable media on system components.

3.8.8 Prohibit the use of portable storage devices when such devices have no identifiable owner.

3.8.9 Protect the confidentiality of backup CUI at storage locations.

For ease of use, the security requirements are organized into fourteen families. Each family contains the requirements related to the general security topic of the family. The families are closely aligned with the minimum-security requirements for federal information and systems described in FIPS 200. The contingency planning, system and services acquisition, and planning requirements are not included within the scope of this publication due to the tailoring criteria. Table 1 lists the security requirement families addressed in this publication.

A discussion section follows each CUI security requirement providing additional information to facilitate the implementation and assessment of the requirements. This information is derived primarily from the security controls discussion sections in SP 800-53 and is provided to give organizations a better understanding of the mechanisms and procedures used to implement the controls used to protect CUI. The discussion section is informative, not normative. It is not intended to extend the scope of a requirement or to influence the solutions organizations may use to satisfy a requirement. The use of examples is notional, not exhaustive, and not reflective of potential options available to organizations. Figure 1 illustrates basic security requirement 3.8.3 with its supporting discussion section and informative references.

3. The Requirements

Security Requirements for Protecting the Confidentiality of CUI

This chapter describes fourteen families of recommended security requirements for protecting the confidentiality of CUI in nonfederal systems and organizations. The security controls from SP 800-53 associated with the basic and derived requirements are

listed in Appendix D. Organizations can use the NIST publication to obtain additional, non- prescriptive information related to the recommended security requirements (e.g., explanatory information in the discussion section for each of the referenced security controls, mapping tables to ISO 27001 security controls, and a catalog of optional controls that can be used to specify additional security requirements, if needed). This information can help clarify or interpret the requirements in the context of mission and business requirements, operational environments, or assessments of risk. Nonfederal organizations can implement a variety of potential security solutions either directly or using managed services, to satisfy the security requirements and may implement alternative, but equally effective, security measures to compensate for the inability to satisfy a requirement.

Nonfederal organizations describe, in a system security plan, how the security requirements are met or how organizations plan to meet the requirements and address known and anticipated threats. The system security plan describes: the system boundary; operational environment; how security requirements are implemented; and the relationships with or connections to other systems. Nonfederal organizations develop plans of action that describe how unimplemented security requirements will be met and how any planned mitigations will be implemented. Organizations can document the system security plan and the plan of action as separate or combined documents and in any chosen format.

When requested, the system security plan (or extracts thereof) and the associated plans of action for any planned implementations or mitigations are submitted to the responsible federal agency/contracting office to demonstrate the nonfederal organization’s implementation or planned implementation of the security requirements. Federal agencies may consider the submitted system security plans and plans of action as critical inputs to a risk management decision to process, store, or transmit CUI on a system hosted by a nonfederal organization and whether it is advisable to pursue an agreement or contract with the nonfederal organization.

The recommended security requirements in this publication apply only to the components of nonfederal systems that process, store, or transmit CUI or that provide protection for such components. Some systems, including specialized systems (e.g., industrial/process control systems, medical devices, Computer Numerical Control machines), may have limitations on the application of certain security requirements.

To accommodate such issues, the system security plan, as reflected in requirement 3.12.4, is used to describe any enduring exceptions to the security requirements. Individual, isolated, or temporary deficiencies are managed though plans of action, as reflected in requirement 3.12.2.

Control Families

3.7: Maintenance

In general, system maintenance requirements tend to support the security objective of availability. However, improper system maintenance or a failure to perform maintenance can result in the unauthorized disclosure of CUI, thus compromising confidentiality of that information.