Ongoing monitoring of the audit activities is the most important activity to include as part of the quality assurance (QA) program requirements for an internal audit department. An IS auditor should perform regular reviews and evaluations of the audit processes, methods, standards, and outcomes to ensure that they comply with the QA program objectives and criteria. This will help to maintain and improve the quality and consistency of the audit services and deliverables. The other options are less important activities to include as part of the QA program requirements, as they may involve long-term resource planning, user satisfaction reports, or feedback from internal audit staff. References:
* CISA Review Manual (Digital Version), Chapter 2, Section 2.61
* CISA Review Questions, Answers & Explanations Database, Question ID 224

The primary purpose of obtaining a baseline image during an operating system audit is to identify atypical running processes. A baseline image is a snapshot of the normal state and configuration of an operating system, including the processes that are expected to run on it. By comparing the current state of the operating system with the baseline image, an IS auditor can detect any deviations or anomalies that may indicate unauthorized or malicious activity, such as malware infection, privilege escalation, or data exfiltration. A baseline image can also help an IS auditor to assess the performance and efficiency of the operating system, as well as its compliance with security standards and policies.
Verifying antivirus definitions (option B) is not the primary purpose of obtaining a baseline image, although it may be a part of the baseline configuration. Antivirus definitions are the files that contain the signatures and rules for detecting and removing malware. An IS auditor may verify that the antivirus definitions are up to date and consistent across the operating system, but this does not require obtaining a baseline image.
Identifying local administrator account access (option C) is not the primary purpose of obtaining a baseline image, although it may be a part of the baseline configuration. Local administrator accounts are user accounts that have full control over the operating system and its resources. An IS auditor may identify and review the local administrator accounts to ensure that they are properly secured and authorized, but this does not require obtaining a baseline image.
Verifying the integrity of operating system backups (option D) is not the primary purpose of obtaining a baseline image, although it may be a part of the backup process. Operating system backups are copies of the operating system data and settings that can be used to restore the system in case of failure or disaster. An IS auditor may verify that the operating system backups are complete, accurate, and accessible, but this does not require obtaining a baseline image.
References: : Linux security and system hardening checklist : CISA Certification | Certified Information Systems Auditor | ISACA : CISA Certified Information Systems Auditor Study Guide, 4th Edition : CISA - Certified Information Systems Auditor Study Guide [Book]

Requiring written authorization for all payment transactions is the IS auditor's best recommendation for a compensating control in an environment where segregation of duties (SoD) cannot be enforced in an accounts payable system. SoD is a principle that requires different individuals or functions to perform different tasks or roles in a business process, such as initiating, approving, recording and reconciling transactions. SoD reduces the risk of errors, fraud and misuse of resources by preventing any single person or function from having excessive or conflicting authority or responsibility. A compensating control is a control that mitigates or reduces the risk associated with the absence or weakness of another control. Requiring written authorization for all payment transactions is a compensating control that provides an independent verification and approval of each transaction before it is processed by the accounts payable system. This control can help to detect and prevent unauthorized, duplicate or erroneous payments, and to ensure compliance with policies and procedures. The other options are not as effective as option A, as they do not provide an independent verification or approval of payment transactions. Restricting payment authorization to senior staff members is a control that limits the number of people who can authorize payments, but it does not prevent them from initiating or processing payments themselves, which could violate SoD. Reconciling payment transactions with invoices is a control that verifies that the payments match the invoices, but it does not prevent unauthorized, duplicate or erroneous payments from being processed by the accounts payable system.
Reviewing payment transaction history is a control that monitors and analyzes thepayment transactions after they have been processed by the accounts payable system, but it does not prevent unauthorized, duplicate or erroneous payments from occurring in the first place. References: CISA Review Manual (Digital Version) , Chapter 5: Protection of Information Assets, Section 5.2: Logical Access.