Using a standardized control framework enables auditors to conduct gap analyses of what a cloud service provider (CSP) offers versus what the customer requires. A standardized control framework is a set of guidelines, best practices, and criteria that help to evaluate and improve the security, privacy, and compliance of cloud computing environments. Examples of standardized control frameworks include ISO/IEC
27001/27002/27017/27018, NIST SP 800-53, CSA Cloud Controls Matrix (CCM), COBIT, etc. By using a standardized control framework, auditors can compare the CSP's policies, procedures, and practices with the customer's expectations and requirements, and identify any gaps or discrepancies that may pose risks or issues. A gap analysis can help the auditors to provide recommendations and suggestions to the CSP and the customer on how to close the gaps and enhance the quality and performance of the cloud services12.
References:
* Cloud Controls Matrix (CCM) - CSA
* Cloud Computing Audit Program - ISACA

In the context of cloud operationalization, "below the waterline" refers to the aspects of cloud services that are managed and controlled by the cloud service provider (CSP) rather than the customer. This analogy is often used to describe the shared responsibility model in cloud computing, where the CSP is responsible for the infrastructure's security and stability, akin to the submerged part of an iceberg that supports the structure above water. The customer, on the other hand, is responsible for managing the controls and security measures
"above the waterline," which include the applications, data, and access management they deploy in the cloud environment.
References = The information provided is based on standard cloud computing models and the shared responsibility concept, which is a fundamental principle discussed in cloud auditing and security literature, including the CCAK curriculum and related resources1.

An organization employing the Cloud Controls Matrix (CCM) to perform a compliance assessment leverages the Scope Applicability direct mapping to understand which controls encompassed by the CCM may already be partially or fully implemented because of the compliance with other standards. The Scope Applicability direct mapping is a worksheet within the CCM that maps the CCM control specifications to several standards within the ISO/IEC 27000 series, such as ISO/IEC 27001, ISO/IEC 27002, ISO/IEC 27017, and ISO/IEC
27018. The mapping helps the organization to identify the commonalities and differences between the CCM and the ISO/IEC standards, and to determine the level of compliance with each standard based on the implementation of the CCM controls. The mapping also helps the organization to avoid duplication of work and to streamline the compliance assessment process.12 References := What you need to know: Transitioning CSA STAR for Cloud Controls Matrix ...1; Cloud Controls Matrix (CCM) - CSA3

During the cloud service provider evaluation process, benchmark controls lists BEST help identify baseline configuration requirements. Benchmark controls lists are standardized sets of security and compliance controls that are applicable to different cloud service models, deployment models, and industry sectors1. They provide a common framework and language for assessing and comparing the security posture and capabilities of cloud service providers2. They also help cloud customers to define their own security and compliance requirements and expectations based on best practices and industry standards3.
Some examples of benchmark controls lists are:
* The Cloud Security Alliance (CSA) Cloud Controls Matrix (CCM), which is a comprehensive list of
133 control objectives that cover 16 domains of cloud security4.
* The National Institute of Standards and Technology (NIST) Special Publication 800-53, which is a catalog of 325 security and privacy controls for federal information systems and organizations, including cloud-based systems5.
* The International Organization for Standardization (ISO) / International Electrotechnical Commission (IEC) 27017, which is a code of practice that provides guidance on 121 information security controls for cloud services based on ISO/IEC 270026.
Vendor requirements, product benchmarks, and contract terms and conditions are not the best sources for identifying baseline configuration requirements. Vendor requirements are the specifications and expectations that the cloud service provider has for its customers, such as minimum hardware, software, network, or support requirements7. Product benchmarks are the measurements and comparisons of the performance, quality, or features of different cloud services or products8. Contract terms and conditions are the legal agreements that define the rights, obligations, and responsibilities of the parties involved in a cloud service contract9. These sources may provide some information on the configuration requirements, but they are not as comprehensive, standardized, or objective as benchmark controls lists.
References:
* CSA Security Guidance for Cloud Computing | CSA1, section on Identify necessary security and compliance requirements
* Evaluation Criteria for Cloud Infrastructure as a Service - Gartner2, section on Security Controls
* Checklist: Cloud Services Provider Evaluation Criteria | Synoptek3, section on Security
* Cloud Controls Matrix | CSA4, section on Overview
* NIST Special Publication 800-53 - NIST Pages5, section on Abstract
* ISO/IEC 27017:2015(en), Information technology - Security techniques ...6, section on Scope
* What is vendor management? Definition from WhatIs.com7, section on Vendor management
* What is Benchmarking? Definition from WhatIs.com8, section on Benchmarking
* What is Terms and Conditions? Definition from WhatIs.com9, section on Terms and Conditions

The auditor's next course of action should be to review the contract and DR capability of the cloud service provider. The contract should specify the roles and responsibilities of both parties regarding disaster recovery, as well as the service level agreements (SLAs) and recovery time objectives (RTOs) for the critical application. The DR capability should demonstrate that the cloud service provider has a plan that is aligned with the organization's requirements and expectations, and that it is tested annually and validated by independent auditors. The auditor should also verify that the organization has a process to monitor and review the cloud service provider's performance and compliance with the contract and SLAs.
Planning an audit of the provider (B) may not be feasible or necessary, as the auditor 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 auditor should rely on the provider's audit reports and certifications to assess their compliance with relevant standards and regulations.
Reviewing the security white paper of the provider may not be sufficient or relevant, as the security white paper may not cover the specific aspects of disaster recovery for the critical application, or may not reflect the current state of the provider's security controls and practices. The security white paper may also be biased or outdated, as it is produced by the provider themselves.
Reviewing the provider's audit reports (D) may be helpful, but not enough, as the audit reports may not address the specific requirements and expectations of the organization for disaster recovery, or may not cover the latest changes or incidents that may affect the provider's DR capability. The audit reports may also have limitations or qualifications that may affect their reliability or validity. References :=
* Audit a Disaster Recovery Plan | AlertFind
* ISACA Introduces New Audit Programs for Business Continuity/Disaster ...
* How to Maintain and Test a Business Continuity and Disaster Recovery Plan