AC-20 Use of External Information Systems (L) (M) (H)

NIST 800-53 (r4) Control:

The organization establishes terms and conditions, consistent with any trust relationships established with other organizations owning, operating, and/or maintaining external information systems, allowing authorized individuals to:

a. Access the information system from external information systems; and

b. Process, store, or transmit organization-controlled information using external information systems.

NIST 800-53 (r4) Supplemental Guidance:

External information systems are information systems or components of information systems that are outside of the authorization boundary established by organizations and for which organizations typically have no direct supervision and authority over the application of required security controls or the assessment of control effectiveness. External information systems include, for example: (i) personally owned information systems/devices (e.g., notebook computers, smart phones, tablets, personal digital assistants); (ii) privately owned computing and communications devices resident in commercial or public facilities (e.g., hotels, train stations, convention centers, shopping malls, or airports); (iii) information systems owned or controlled by nonfederal governmental organizations; and (iv) federal information systems that are not owned by, operated by, or under the direct supervision and authority of organizations. This control also addresses the use of external information systems for the processing, storage, or transmission of

organizational information, including, for example, accessing cloud services (e.g., infrastructure as a service, platform as a service, or software as a service) from organizational information systems.

For some external information systems (i.e., information systems operated by other federal agencies, including organizations subordinate to those agencies), the trust relationships that have been established between those organizations and the originating organization may be such, that no explicit terms and conditions are required. Information systems within these organizations

would not be considered external. These situations occur when, for example, there are pre-existing sharing/trust agreements (either implicit or explicit) established between federal agencies or organizations subordinate to those agencies, or when such trust agreements are specified by applicable laws, Executive Orders, directives, or policies. Authorized individuals include, for example, organizational personnel, contractors, or other individuals with authorized access to organizational information systems and over which organizations have the authority to impose rules of behavior with regard to system access. Restrictions that organizations impose on authorized individuals need not be uniform, as those restrictions may vary depending upon the

trust relationships between organizations. Therefore, organizations may choose to impose different security restrictions on contractors than on state, local, or tribal governments.

This control does not apply to the use of external information systems to access public interfaces to organizational information systems (e.g., individuals accessing federal information through www.usa.gov). Organizations establish terms and conditions for the use of external information systems in accordance with organizational security policies and procedures. Terms and conditions address as a minimum: types of applications that can be accessed on organizational information systems from external information systems; and the highest security category of information that can be processed, stored, or transmitted on external information systems. If terms and conditions with the owners of external information systems cannot be established, organizations may impose restrictions on organizational personnel using those external systems. Related controls: AC-3, AC-17, AC-19, CA-3, PL-4, SA-9.

References: FIPS Publication 199.

NIST 800-53 (r5) Discussion:

External systems are systems that are used by but not part of organizational systems, and for which the organization has no direct control over the implementation of required controls or the assessment of control effectiveness. External systems include personally owned systems, components, or devices; privately owned computing and communications devices in commercial or public facilities; systems owned or controlled by nonfederal organizations; systems managed by contractors; and federal information systems that are not owned by, operated by, or under the direct supervision or authority of the organization. External systems also include systems owned or operated by other components within the same organization and systems within the organization with different authorization boundaries. Organizations have the option to prohibit the use of any type of external system or prohibit the use of specified types of external systems, (e.g., prohibit the use of any external system that is not organizationally owned or prohibit the use of personally-owned systems).

For some external systems (i.e., systems operated by other organizations), the trust relationships that have been established between those organizations and the originating organization may be such that no explicit terms and conditions are required. Systems within these organizations may not be considered external. These situations occur when, for example, there are pre-existing information exchange agreements (either implicit or explicit) established between organizations or components or when such agreements are specified by applicable laws, executive orders, directives, regulations, policies, or standards. Authorized individuals include organizational personnel, contractors, or other individuals with authorized access to organizational systems and over which organizations have the authority to impose specific rules of behavior regarding system access. Restrictions that organizations impose on authorized individuals need not be uniform, as the restrictions may vary depending on trust relationships between organizations. Therefore, organizations may choose to impose different security restrictions on contractors than on state, local, or tribal governments.

External systems used to access public interfaces to organizational systems are outside the scope of AC-20. Organizations establish specific terms and conditions for the use of external systems in accordance with organizational security policies and procedures. At a minimum, terms and conditions address the specific types of applications that can be accessed on organizational systems from external systems and the highest security category of information that can be processed, stored, or transmitted on external systems. If the terms and conditions with the owners of the external systems cannot be established, organizations may impose restrictions on organizational personnel using those external systems.

38North Guidance:

Meets Minimum Requirement:

• Terms, and conditions along with trust relationships need to be established if the FedRAMP production environment can be accessed from another external system that is not controlled by the organization.

Best Practice:

• Only permit personnel to access the information system from other external systems only if documented proper authorizations are in place such as SLA, MOU, ISA etc.

Unofficial FedRAMP Guidance: None.

Assessment Evidence:

• Examples of SLA, MOU, ISA with external parties that can access the FedRAMP system their organization.

CSP Implementation Tips:

• Amazon Web Services (AWS): TBD

• Microsoft Azure: TBD

• Google Cloud Platform: TBD