While SLAs, MOUs, and BPAs are important in various business contexts, they do not specifically address the security requirements for network interconnections between organizations. An ISA is the most appropriate agreement for defining security controls in this scenario.
An Interconnection Security Agreement (ISA) should be implemented in this scenario. An ISA is a security document that specifies the technical and security requirements for establishing, operating, and maintaining a connection between two or more IT systems belonging to different organizations. In this case, where a third-party vendor is connecting directly to the company’s internal network, an ISA is crucial to define the security controls, protocols, and responsibilities of both parties. The ISA would typically include details such as the purpose of the interconnection, the services offered, the security controls required (e.g., encryption, access controls, monitoring), the responsibilities of each party in maintaining security, incident response procedures, and the duration of the agreement. This helps ensure that the connection does not introduce unnecessary risks to either party’s network and that both parties understand their roles in maintaining the security of the interconnection.