Certified Information Systems Auditor Practice Exam 2025 - Free CISA Practice Questions and Study Guide

An IS auditor should determine the high-risk systems and plan accordingly because this approach allows for a targeted and efficient use of audit resources. By identifying systems that are critical to the organization's operations and pose the highest risk of failure or security breaches, the auditor can focus their efforts where they are most needed. This strategy aligns with the risk-based auditing approach, which emphasizes assessing and managing risks effectively.

Focusing only on recently implemented systems may overlook older, yet still critical systems that could present significant risks. Similarly, conducting an audit on all systems or solely on systems that have had issues is not resource-efficient and may dilute the auditor’s attention from high-risk areas. Additionally, concentrating on training rather than audits would neglect the necessary assessment and evaluation of system controls, which is essential to ensure compliance and effectiveness. Thus, prioritizing high-risk systems allows an auditor to perform a more informed and impactful assessment tailored to the organization's specific risk profile.