A document that regulates the security-related aspects of a planned relationship between an organization and an external system. It regulates the security interface between two systems operating under two different authorities. It contains a variety of descriptive, technical, process engineering and planning information. It is usually preceded by a formal Memorandum of Understanding/Understanding that defines senior-level roles and responsibilities in managing a cross-domain connection. Source(s): SCISS 4009-2015 This guide establishes an agreement between organizations that own and operate connected IT systems to document the technical requirements of interconnection. IAPH also supports a Memorandum of Understanding (MOU/A) between organizations. Source(s): NIST SP 800-47 under the Interconnection Security Agreement (ISA) Comments on the glossary layout and functionality should be sent to secglossary@nist.gov. Comments on specific definitions should be sent to the authors of the linked source publication. For NIST publications, there is usually an email inside the document. .