The most useful document for an auditor to review when seeking visibility into the cloud supply chain for a newly acquired Software as a Service (SaaS) solution is the SaaS provider contract. The contract is the legal agreement that defines the terms and conditions of the cloud service, including the roles, responsibilities, and obligations of the parties involved1. The contract should also specify the service level agreements (SLAs), security and privacy requirements, data ownership and governance, incident response and reporting, audit rights and access, and subcontracting or outsourcing arrangements of the SaaS provider2. By reviewing the contract, the auditor can gain insight into the cloud supply chain and assess the risks, controls, and compliance of the SaaS solution.
The other options are not as useful as the SaaS provider contract. Payments made by the service owner are the financial transactions that reflect the fees or charges incurred by using the SaaS solution. They may indicate the usage or consumption of the cloud service, but they do not provide much information about the cloud supply chain or its security and compliance aspects3. SaaS vendor white papers are the marketing or educational materials that describe the features, benefits, or best practices of the SaaS solution. They may provide some general or technical information about the cloud service, but they are not legally binding or verifiable4. Cloud compliance obligations register is a tool that helps customers identify and track their compliance requirements and obligations for using cloud services. It may help customers understand their own responsibilities and risks in relation to the cloud service, but it does not necessarily reflect the compliance status or performance of the SaaS provider5.
References:
Cloud Services Due Diligence Checklist | Trust Center1, section on How to use the checklist
Cloud Computing Security Considerations | Cyber.gov.au2, section on Contractual arrangements
Cloud Computing Pricing Models: A Comparison - DZone Cloud3, section on Pricing Models
What is a White Paper? Definition from WhatIs.com4, section on White Paper
Cloud Compliance Obligations Register | Cyber.gov.au5, section on Cloud Compliance Obligations Register