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

All such third party systems must be registered with the system. Please use this checklist to register new third-party systems.