This requirement addresses the termination of user-initiated logical sessions in contrast to the termination of network connections that are associated with communications sessions (i.e., disconnecting from the network). A logical session (for local, network, and remote access) is initiated whenever a user (or process acting on behalf of a user) accesses an organizational system. Such user sessions can be terminated (and thus terminate user access) without terminating network sessions. Session termination terminates all processes associated with a user’s logical session except those processes that are specifically created by the user (i.e., session owner) to continue after the session is terminated. Conditions or trigger events requiring automatic session termination can include organization-defined periods of user inactivity, targeted responses to certain types of incidents, and time-of-day restrictions on system use

Remote access is access to organizational systems by users (or processes acting on behalf of users) communicating through external networks (e.g., the Internet). Remote access methods include dial-up, broadband, and wireless. Organizations often employ encrypted virtual private networks (VPNs) to enhance confidentiality over remote connections. The use of encrypted VPNs does not make the access non-remote; however, the use of VPNs, when adequately provisioned with appropriate control (e.g., employing encryption techniques for confidentiality protection), may provide sufficient assurance to the organization that it can effectively treat such connections as internal networks. VPNs with encrypted tunnels can affect the capability to adequately monitor network communications traffic for malicious code. Automated monitoring and control of remote access sessions allows organizations to detect cyber-attacks and help to ensure ongoing compliance with remote access policies by auditing connection activities of remote users on a variety of system components (e.g., servers, workstations, notebook computers, smart phones, and tablets). [SP 800-46], [SP 800-77], and [SP 800-113] provide guidance on secure remote access and virtual private networks.

Cryptographic standards include FIPS-validated cryptography and NSA-approved cryptography. See [NIST CRYPTO]; [NIST CAVP]; [NIST CMVP]; National Security Agency Cryptographic Standards.

Routing remote access through managed access control points enhances explicit, organizational control over such connections, reducing the susceptibility to unauthorized access to organizational systems resulting in the unauthorized disclosure of CUI.

A privileged command is a human-initiated (interactively or via a process operating on behalf of the human) command executed on a system involving the control, monitoring, or administration of the system including security functions and associated security-relevant information. Security-relevant information is any information within the system that can potentially impact the operation of security functions or the provision of security services in a manner that could result in failure to enforce the system security policy or maintain isolation of code and data. Privileged commands give individuals the ability to execute sensitive, security-critical, or security-relevant system functions. Controlling such access from remote locations helps to ensure that unauthorized individuals are not able to execute such commands freely with the potential to do serious or catastrophic damage to organizational systems. Note that the ability to affect the integrity of the system is considered security-relevant as that could enable the means to by-pass security functions although not directly impacting the function itself.

Establishing usage restrictions and configuration/connection requirements for wireless access to the system provides criteria for organizations to support wireless access authorization decisions. Such restrictions and requirements reduce the susceptibility to unauthorized access to the system through wireless technologies. Wireless networks use authentication protocols which provide credential protection and mutual authentication. [SP 800-97] provides guidance on secure wireless networks.

Organizations authenticate individuals and devices to help protect wireless access to the system. Special attention is given to the wide variety of devices that are part of the Internet of Things with potential wireless access to organizational systems. See [NIST CRYPTO].

A mobile device is a computing device that has a small form factor such that it can easily be carried by a single individual; is designed to operate without a physical connection (e.g., wirelessly transmit or receive information); possesses local, non-removable or removable data storage; and includes a self-contained power source. Mobile devices may also include voice communication capabilities, on-board sensors that allow the device to capture information, or built-in features for synchronizing local data with remote locations. Examples of mobile devices include smart phones, e-readers, and tablets. Due to the large variety of mobile devices with different technical characteristics and capabilities, organizational restrictions may vary for the different types of devices. Usage restrictions and implementation guidance for mobile devices include: device identification and authentication; configuration management; implementation of mandatory protective software (e.g., malicious code detection, firewall); scanning devices for malicious code; updating virus protection software; scanning for critical software updates and patches; conducting primary operating system (and possibly other resident software) integrity checks; and disabling unnecessary hardware (e.g., wireless, infrared). The need to provide adequate security for mobile devices goes beyond this requirement. Many controls for mobile devices are reflected in other CUI security requirements. [SP 800-124] provides guidance on mobile device security.

Organizations can employ full-device encryption or container-based encryption to protect the confidentiality of CUI on mobile devices and computing platforms. Container-based encryption provides a more fine-grained approach to the encryption of data and information including encrypting selected data structures such as files, records, or fields. See [NIST CRYPTO]. [23] Mobile devices and computing platforms include, for example, smartphones and tablets.

External systems are systems or components of systems for which organizations typically have no direct supervision and authority over the application of security requirements and controls or the determination of the effectiveness of implemented controls on those systems. External systems include personally owned systems, components, or devices and privately-owned computing and communications devices resident in commercial or public facilities.

This requirement also addresses the use of external systems for the processing, storage, or transmission of CUI, including accessing cloud services (e.g., infrastructure as a service, platform as a service, or software as a service) from organizational systems. Organizations establish terms and conditions for the use of external systems in accordance with organizational security policies and procedures. Terms and conditions address as a minimum, the types of applications that can be accessed on organizational systems from external systems.

If terms and conditions with the owners of external systems cannot be established, organizations may impose restrictions on organizational personnel using those external systems. This requirement recognizes that there are circumstances where individuals using external systems (e.g., contractors, coalition partners) need to access organizational systems. In those situations, organizations need confidence that the external systems contain the necessary controls so as not to compromise, damage, or otherwise harm organizational systems.

Verification that the required controls have been effectively implemented can be achieved by third-party, independent assessments, attestations, or other means, depending on the assurance or confidence level required by organizations. Note that while “external” typically refers to outside of the organization’s direct supervision and authority, that is not always the case.

Regarding the protection of CUI across an organization, the organization may have systems that process CUI and others that do not. And among the systems that process CUI there are likely access restrictions for CUI that apply between systems. Therefore, from the perspective of a given system, other systems within the organization may be considered “external" to that system.