The most important thing to verify before entering into a relationship with a third party to host sensitive archived data is the vendor's controls are in line with the organization's security standards. This is because the organization is ultimately responsible for the security and privacy of its data, even if it is stored or processed by a third party. The organization should ensure that the vendor has adequate and effective controls to protect the data from unauthorized access, modification, disclosure, or destruction. The organization should also ensure that the vendor complies with the applicable laws and regulations regarding data protection, such as the General Data Protection Regulation (GDPR) in the European Union. The organization should conduct a thorough risk assessment of the vendor and its services, and establish a clear contract that defines the roles, responsibilities, expectations, and obligations of both parties.
References = CISM Review Manual 15th Edition, Chapter 3, Section 3.2.1, page 1341; CISM Review Questions, Answers & Explanations Manual 9th Edition, Question 2, page 2