The best option to protect against a future recurrence of unauthorized access by a service provider’s administrator is D. Contractual requirements. Data encryption, intrusion prevention system, and two-factor authentication are all technical measures that can enhance the security of the data stored in the Infrastructure as a Service (IaaS) model, but they do not prevent the service provider’s administrator from accessing the data if they have the necessary credentials, keys, or permissions. Contractual requirements, on the other hand, are legal obligations that bind the service provider to respect the customer’s privacy and confidentiality, and to limit the access tothe data to only authorized and necessary personnel. Contractual requirements can also specify the penalties or remedies for any breach of contract, which can deter the service provider’s administrator from violating the terms of the agreement. Therefore, contractual requirements are the most effective way to protect against a future recurrence of unauthorized access by a service provider’s administrator12

1: What is Data Encryption? | Forcepoint 2: The elements of a contract: understanding contract requirements - Juro