Review of security metrics trends is the best evidence to senior management that security control performance has improved because it helps to measure and demonstrate the effectiveness and efficiency of the security controls over time. Security metrics are quantitative or qualitative indicators that provide information about the security status or performance of an organization, system, process, or activity. Security metrics can be used to evaluate the implementation, operation, and outcome of security controls, such as the number of vulnerabilities detected and remediated, the time to respond and recover from incidents, the compliance level with security policies and standards, or the return on security investment. Review of security metrics trends helps to identify and communicate the progress, achievements, and challenges of the security program, as well as to support decision making and continuous improvement. Therefore, review of security metrics trends is the correct answer.
References:
https://www.bitsight.com/blog/importance-continuous-improvement-security-performance-management
https://www.isaca.org/resources/isaca-journal/issues/2020/volume-6/key-performance-indicators-for-security- governance-part-2
https://www.nist.gov/news-events/news/2021/09/dhs-nist-coordinate-releasing-preliminary-cybersecurity- performance-goals.

Information security program metrics are the best way to demonstrate the status of an organization's information security program to the board of directors, as they provide relevant and meaningful information on the performance, effectiveness, and value of the program, as well as the current and emerging risks and the corresponding mitigation strategies. Information security program metrics should be aligned with the business objectives and risk appetite of the organization, and should be presented in a clear and concise manner that enables the board of directors to make informed decisions and provide oversight. (From CISM Review Manual 15th Edition) References: CISM Review Manual 15th Edition, page 37, section 1.3.2.2.

Information security governance is the process of establishing and maintaining a framework to provide assurance that information security strategies are aligned with business objectives and consistent with applicable laws and regulations. In addition to executive sponsorship and business alignment, a critical factor for effective information security governance is ownership of security, which means that the roles and responsibilities for information security are clearly defined and assigned to the appropriate stakeholders, such as business owners, information owners, information custodians, and users. Ownership of security also implies accountability for the protection of information assets and the management of security risks.
References: https://www.isaca.org/credentialing/cism https://www.nist.gov/publications/information-security- handbook-guide-managers

Cost-benefit analysis of mitigating controls is the BEST way to assist in determining whether to accept residual risk of a critical security system, because it helps to compare the costs of implementing and maintaining the controls with the benefits of reducing the risk and the potential losses. Cost-benefit analysis can help to justify the investment in security controls and to optimize the level of residual risk that is acceptable for the organization.
References =
CISM Review Manual, 16th Edition, ISACA, 2020, p. 50: "Cost-benefit analysis is the process of comparing the costs of risk treatment options with the benefits of risk reduction and the potential losses from risk events." CISM Review Manual, 16th Edition, ISACA, 2020, p. 51: "Cost-benefit analysis can help to justify the investment in information security controls and to optimize the level of residual risk that is acceptable for the enterprise." CISM Domain 2: Information Risk Management (IRM) [2022 update]: "Cost-benefit analysis: This is a comparison of the costs of implementing and maintaining security controls with the benefits of reducing risk and potential losses. It helps to justify the investment in security controls and optimize the level of residual risk."

An information security manager is assisting in the development of the request for proposal (RFP) for a new outsourced service. This will require the third party to have access to critical business information. The security manager should focus primarily on defining security requirements for the process being outsourced.
Security requirements are the specifications of what needs to be done to protect the information assets from unauthorized access, use, disclosure, modification, or destruction. Security requirements should be aligned with the organization's risk appetite and business objectives, and should cover both technical and organizational aspects of the service delivery. Security requirements should also be clear, concise, measurable, achievable, realistic, and testable. References = CISM Review Manual (Digital Version), Chapter
3: Information Security Risk Management, Section 3.1: Risk Identification, p. 115-1161. CISM Review Manual (Print Version), Chapter 3: Information Security Risk Management, Section 3.1: Risk Identification, p. 115-1162. CISM ITEM DEVELOPMENT GUIDE, Domain 3: Information Security Program Development and Management, Task Statement 3.1, p. 193.
Security requirements for the process being outsourced are the specifications and standards that the third party must comply with to ensure the confidentiality, integrity and availability of the critical business information.
They define the roles and responsi-bilities of both parties, the security controls and measures to be implemented, the se-curity objectives and expectations, the security risks and mitigation strategies, and the security monitoring and reporting mechanisms. Security requirements are essential to protect the information assets of the organization and to establish a clear and en-forceable contractual relationship with the third party.
References:
*1 Outsourcing Strategies for Information Security: Correlated Losses and Security Exter-nalities - SpringerLink
*2 What requirements must outsourcing services comply with for the European market? - CBI
*3 Outsourcing cybersecurity: What services to outsource, what to keep in house - Infosec Institute
*4 BCFSA outsourcing and information security guidelines - BLG