NIST SP 800-53 Rev. 5 Common Control Library

NIST control statement

a. Configure the system to provide only [Assignment: mission-essential capabilities] ; and b. Prohibit or restrict the use of the following functions, ports, protocols, software, and/or services: [Assignment: organization-defined prohibited or restricted functions, system ports, protocols, software, and/or services].

Discussion

Systems provide a wide variety of functions and services. Some of the functions and services routinely provided by default may not be necessary to support essential organizational missions, functions, or operations. Additionally, it is sometimes convenient to provide multiple services from a single system component, but doing so increases risk over limiting the services provided by that single component. Where feasible, organizations limit component functionality to a single function per component. Organizations consider removing unused or unnecessary software and disabling unused or unnecessary physical and logical ports and protocols to prevent unauthorized connection of components, transfer of information, and tunneling. Organizations employ network scanning tools, intrusion detection and prevention systems, and end-point protection technologies, such as firewalls and host-based intrusion detection systems, to identify and prevent the use of prohibited functions, protocols, ports, and services. Least functionality can also be achieved as part of the fundamental design and development of the system (see [SA-8](#sa-8), [SC-2](#sc-2) , and [SC-3](#sc-3)).

NIST control statement

Manage system authenticators by: a. Verifying, as part of the initial authenticator distribution, the identity of the individual, group, role, service, or device receiving the authenticator; b. Establishing initial authenticator content for any authenticators issued by the organization; c. Ensuring that authenticators have sufficient strength of mechanism for their intended use; d. Establishing and implementing administrative procedures for initial authenticator distribution, for lost or compromised or damaged authenticators, and for revoking authenticators; e. Changing default authenticators prior to first use; f. Changing or refreshing authenticators [Assignment: time period by authenticator type] or when [Assignment: events] occur; g. Protecting authenticator content from unauthorized disclosure and modification; h. Requiring individuals to take, and having devices implement, specific controls to protect authenticators; and i. Changing authenticators for group or role accounts when membership to those accounts changes.

Discussion

Authenticators include passwords, cryptographic devices, biometrics, certificates, one-time password devices, and ID badges. Device authenticators include certificates and passwords. Initial authenticator content is the actual content of the authenticator (e.g., the initial password). In contrast, the requirements for authenticator content contain specific criteria or characteristics (e.g., minimum password length). Developers may deliver system components with factory default authentication credentials (i.e., passwords) to allow for initial installation and configuration. Default authentication credentials are often well known, easily discoverable, and present a significant risk. The requirement to protect individual authenticators may be implemented via control [PL-4](#pl-4) or [PS-6](#ps-6) for authenticators in the possession of individuals and by controls [AC-3](#ac-3), [AC-6](#ac-6) , and [SC-28](#sc-28) for authenticators stored in organizational systems, including passwords stored in hashed or encrypted formats or files containing encrypted or hashed passwords accessible with administrator privileges. Systems support authenticator management by organization-defined settings and restrictions for various authenticator characteristics (e.g., minimum password length, validation time window for time synchronous one-time tokens, and number of allowed rejections during the verification stage of biometric authentication). Actions can be taken to safeguard individual authenticators, including maintaining possession of authenticators, not sharing authenticators with others, and immediately reporting lost, stolen, or compromised authenticators. Authenticator management includes issuing and revoking authenticators for temporary access when no longer needed.

NIST control statement

Design the security and privacy architectures for the system using a defense-in-depth approach that: (a) Allocates [Assignment: controls] to [Assignment: locations and architectural layers] ; and (b) Ensures that the allocated controls operate in a coordinated and mutually reinforcing manner.

Discussion

Organizations strategically allocate security and privacy controls in the security and privacy architectures so that adversaries must overcome multiple controls to achieve their objective. Requiring adversaries to defeat multiple controls makes it more difficult to attack information resources by increasing the work factor of the adversary; it also increases the likelihood of detection. The coordination of allocated controls is essential to ensure that an attack that involves one control does not create adverse, unintended consequences by interfering with other controls. Unintended consequences can include system lockout and cascading alarms. The placement of controls in systems and organizations is an important activity that requires thoughtful analysis. The value of organizational assets is an important consideration in providing additional layering. Defense-in-depth architectural approaches include modularity and layering (see [SA-8(3)](#sa-8.3) ), separation of system and user functionality (see [SC-2](#sc-2) ), and security function isolation (see [SC-3](#sc-3)).

NIST control statement

Separate user functionality, including user interface services, from system management functionality.

Discussion

System management functionality includes functions that are necessary to administer databases, network components, workstations, or servers. These functions typically require privileged user access. The separation of user functions from system management functions is physical or logical. Organizations may separate system management functions from user functions by using different computers, instances of operating systems, central processing units, or network addresses; by employing virtualization techniques; or some combination of these or other methods. Separation of system management functions from user functions includes web administrative interfaces that employ separate authentication methods for users of any other system resources. Separation of system and user functions may include isolating administrative interfaces on different domains and with additional access controls. The separation of system and user functionality can be achieved by applying the systems security engineering design principles in [SA-8](#sa-8) , including [SA-8(1)](#sa-8.1), [SA-8(3)](#sa-8.3), [SA-8(4)](#sa-8.4), [SA-8(10)](#sa-8.10), [SA-8(12)](#sa-8.12), [SA-8(13)](#sa-8.13), [SA-8(14)](#sa-8.14) , and [SA-8(18)](#sa-8.18).

NIST control statement

Prevent the presentation of system management functionality at interfaces to non-privileged users.

Discussion

Preventing the presentation of system management functionality at interfaces to non-privileged users ensures that system administration options, including administrator privileges, are not available to the general user population. Restricting user access also prohibits the use of the grey-out option commonly used to eliminate accessibility to such information. One potential solution is to withhold system administration options until users establish sessions with administrator privileges.

NIST control statement

Store state information from applications and software separately.

Discussion

If a system is compromised, storing applications and software separately from state information about users’ interactions with an application may better protect individuals’ privacy.

NIST control statement

a. Provide additional data origin authentication and integrity verification artifacts along with the authoritative name resolution data the system returns in response to external name/address resolution queries; and b. Provide the means to indicate the security status of child zones and (if the child supports secure resolution services) to enable verification of a chain of trust among parent and child domains, when operating as part of a distributed, hierarchical namespace.

Discussion

Providing authoritative source information enables external clients, including remote Internet clients, to obtain origin authentication and integrity verification assurances for the host/service name to network address resolution information obtained through the service. Systems that provide name and address resolution services include domain name system (DNS) servers. Additional artifacts include DNS Security Extensions (DNSSEC) digital signatures and cryptographic keys. Authoritative data includes DNS resource records. The means for indicating the security status of child zones include the use of delegation signer resource records in the DNS. Systems that use technologies other than the DNS to map between host and service names and network addresses provide other means to assure the authenticity and integrity of response data.

NIST control statement

Withdrawn in this source release; review the official source for disposition.

NIST control statement

Provide data origin and integrity protection artifacts for internal name/address resolution queries.

Discussion

None.

NIST control statement

Request and perform data origin authentication and data integrity verification on the name/address resolution responses the system receives from authoritative sources.

Discussion

Each client of name resolution services either performs this validation on its own or has authenticated channels to trusted validation providers. Systems that provide name and address resolution services for local clients include recursive resolving or caching domain name system (DNS) servers. DNS client resolvers either perform validation of DNSSEC signatures, or clients use authenticated channels to recursive resolvers that perform such validations. Systems that use technologies other than the DNS to map between host and service names and network addresses provide some other means to enable clients to verify the authenticity and integrity of response data.

NIST control statement

Withdrawn in this source release; review the official source for disposition.

NIST control statement

Ensure the systems that collectively provide name/address resolution service for an organization are fault-tolerant and implement internal and external role separation.

Discussion

Systems that provide name and address resolution services include domain name system (DNS) servers. To eliminate single points of failure in systems and enhance redundancy, organizations employ at least two authoritative domain name system servers—one configured as the primary server and the other configured as the secondary server. Additionally, organizations typically deploy the servers in two geographically separated network subnetworks (i.e., not located in the same physical facility). For role separation, DNS servers with internal roles only process name and address resolution requests from within organizations (i.e., from internal clients). DNS servers with external roles only process name and address resolution information requests from clients external to organizations (i.e., on external networks, including the Internet). Organizations specify clients that can access authoritative DNS servers in certain roles (e.g., by address ranges and explicit lists).

NIST control statement

Protect the authenticity of communications sessions.

Discussion

Protecting session authenticity addresses communications protection at the session level, not at the packet level. Such protection establishes grounds for confidence at both ends of communications sessions in the ongoing identities of other parties and the validity of transmitted information. Authenticity protection includes protecting against "man-in-the-middle" attacks, session hijacking, and the insertion of false information into sessions.

NIST control statement

Invalidate session identifiers upon user logout or other session termination.

Discussion

Invalidating session identifiers at logout curtails the ability of adversaries to capture and continue to employ previously valid session IDs.

NIST control statement

Withdrawn in this source release; review the official source for disposition.

NIST control statement

Generate a unique session identifier for each session with [Assignment: randomness requirements] and recognize only session identifiers that are system-generated.

Discussion

Generating unique session identifiers curtails the ability of adversaries to reuse previously valid session IDs. Employing the concept of randomness in the generation of unique session identifiers protects against brute-force attacks to determine future session identifiers.

NIST control statement

Withdrawn in this source release; review the official source for disposition.

NIST control statement

Only allow the use of [Assignment: certificated authorities] for verification of the establishment of protected sessions.

Discussion

Reliance on certificate authorities for the establishment of secure sessions includes the use of Transport Layer Security (TLS) certificates. These certificates, after verification by their respective certificate authorities, facilitate the establishment of protected sessions between web clients and web servers.

NIST control statement

Fail to a [Assignment: known system state] for the following failures on the indicated components while preserving [Assignment: system state information] in failure: [Assignment: types of system failures on system components].

Discussion

Failure in a known state addresses security concerns in accordance with the mission and business needs of organizations. Failure in a known state prevents the loss of confidentiality, integrity, or availability of information in the event of failures of organizational systems or system components. Failure in a known safe state helps to prevent systems from failing to a state that may cause injury to individuals or destruction to property. Preserving system state information facilitates system restart and return to the operational mode with less disruption of mission and business processes.

NIST control statement

Employ minimal functionality and information storage on the following system components: [Assignment: system components].

Discussion

The deployment of system components with minimal functionality reduces the need to secure every endpoint and may reduce the exposure of information, systems, and services to attacks. Reduced or minimal functionality includes diskless nodes and thin client technologies.

NIST control statement

Include components within organizational systems specifically designed to be the target of malicious attacks for detecting, deflecting, and analyzing such attacks.

Discussion

Decoys (i.e., honeypots, honeynets, or deception nets) are established to attract adversaries and deflect attacks away from the operational systems that support organizational mission and business functions. Use of decoys requires some supporting isolation measures to ensure that any deflected malicious code does not infect organizational systems. Depending on the specific usage of the decoy, consultation with the Office of the General Counsel before deployment may be needed.

NIST control statement

Withdrawn in this source release; review the official source for disposition.

NIST control statement

Include within organizational systems the following platform independent applications: [Assignment: platform-independent applications].

Discussion

Platforms are combinations of hardware, firmware, and software components used to execute software applications. Platforms include operating systems, the underlying computer architectures, or both. Platform-independent applications are applications with the capability to execute on multiple platforms. Such applications promote portability and reconstitution on different platforms. Application portability and the ability to reconstitute on different platforms increase the availability of mission-essential functions within organizations in situations where systems with specific operating systems are under attack.

NIST control statement

Protect the [Selection (one-or-more): confidentiality; integrity] of the following information at rest: [Assignment: information at rest].

Discussion

Information at rest refers to the state of information when it is not in process or in transit and is located on system components. Such components include internal or external hard disk drives, storage area network devices, or databases. However, the focus of protecting information at rest is not on the type of storage device or frequency of access but rather on the state of the information. Information at rest addresses the confidentiality and integrity of information and covers user information and system information. System-related information that requires protection includes configurations or rule sets for firewalls, intrusion detection and prevention systems, filtering routers, and authentication information. Organizations may employ different mechanisms to achieve confidentiality and integrity protections, including the use of cryptographic mechanisms and file share scanning. Integrity protection can be achieved, for example, by implementing write-once-read-many (WORM) technologies. When adequate protection of information at rest cannot otherwise be achieved, organizations may employ other controls, including frequent scanning to identify malicious code at rest and secure offline storage in lieu of online storage.

NIST control statement

Implement cryptographic mechanisms to prevent unauthorized disclosure and modification of the following information at rest on [Assignment: system components or media]: [Assignment: information].

Discussion

The selection of cryptographic mechanisms is based on the need to protect the confidentiality and integrity of organizational information. The strength of mechanism is commensurate with the security category or classification of the information. Organizations have the flexibility to encrypt information on system components or media or encrypt data structures, including files, records, or fields.