Which of the following is the MOST critical step when planning an IS audit?

Performing a risk assessment is the most critical step when planning an IS audit because it helps identify and prioritize the potential threats and vulnerabilities that could impact the organization's information systems. By understanding the specific risks associated with the business processes and systems, auditors can tailor their audit plan to focus on the areas that are most likely to pose a challenge to the organization's objectives. This ensures that resources are allocated efficiently and effectively, allowing for a more targeted and relevant audit that addresses the highest risks.

A risk assessment also aligns the audit with the organization's overall risk management strategy and goals, making it imperative for developing a comprehensive audit approach. It sets the foundation for the entire audit process, influencing the scope, objectives, and methodology used during the audit, and ultimately contributes to the reliability and credibility of the audit findings.