The optimal and most efficient mechanism to assess the controls that the provider is responsible for is to review third-party audit reports. Third-party audit reports are independent and objective assessments of the provider’s security, compliance, and performance, conducted by qualified and reputable auditors. Third-party audit reports can provide assurance and evidence that the provider meets the industry standards and best practices, as well as the contractual and legal obligations with the SaaS company. Third-party audit reports can also cover a wide range of controls, such as data security, encryption, identity and access management, incident response, disaster recovery, and service level agreements. Some examples of third-party audit reports are ISO 27001 certification, SOC 1/2/3 reports, CSA STAR certification, and FedRAMP authorization123.
Reviewing the provider’s published questionnaires (A) may not be optimal or efficient, as the published questionnaires may not be comprehensive or up-to-date, and may not reflect the actual state of the provider’s controls. The published questionnaires may also be biased or inaccurate, as they are produced by the provider themselves.
Directly auditing the provider © may not be feasible or necessary, as the independent contractor may not have access to the provider’s environment or data, and may not have the authority or expertise to conduct such an audit. The independent contractor should rely on the third-party audit reports and certifications to assess the provider’s compliance with relevant standards and regulations.
Sending a supplier questionnaire to the provider (D) may not be optimal or efficient, as the supplier questionnaire may not cover all the aspects of the provider’s controls, and may not provide sufficient evidence or assurance of the provider’s security maturity. The supplier questionnaire may also take a long time to complete and verify, and may not be consistent with the industry standards and best practices. References :=
How to Evaluate Cloud Service Provider Security (Checklist)
Cloud service review process - Cloud Adoption Framework
How to choose a cloud service provider | Microsoft Azure
