Full disk encryption (FDE) is a means of protecting information by encrypting all of the data on a disk, including temporary files, programs, and system files1. FDE is best suited for addressing the risk scenario of physical theft of media on which information is stored, as it prevents unauthorized access to the data even if the device is lost or stolen2. FDE does not prevent data leakage as a result of employees leaving to work for competitors, as they may still have access to the data while using the device or copy the data to another device before leaving. FDE does not prevent noncompliance fines related to storage of regulated information, as it does not ensure that the data is stored in accordance with the applicable laws and regulations. FDE does not prevent unauthorized logical access to information through an application interface, as it does not control the access rights and permissions of users and applications. *References: According to the ISACA IT Audit and Assurance Standards, Guidelines and Tools and Techniques for IS Audit and Assurance Professionals, section
2402 Planning, "The IS audit and assurance professional should identify and assess risk relevant to the area under review." 3 One of the risk factors to consider is "the sensitivity of information processed, stored or transmitted by the system" 3. FDE is one of the possible controls to mitigate the risk of unauthorized disclosure of sensitive information due to physical theft of media.

Understanding the business process is the first step an IS auditor needs to perform. Standards do not require an IS auditor to perform a process walkthrough. Identifying control weaknesses is not the primary reason for the walkthrough and typically occurs at a later stage in the audit, while planning for substantive testing is performed at a later stage in the audit.

A test plan for the BCP is essential to ensure that the plan is effective, updated and aligned with the current business needs and objectives. A change in organizational structure with significant impact to business processes may require a revision of the BCP and a new test plan to validate its adequacy. The lack of a test plan for the BCP for two years indicates a high risk of failure in the event ofa disaster or disruption.
Therefore, this should be the auditor's greatest concern among the given options. References:
ISACA, IT Control Objectives for Sarbanes-Oxley, 4th Edition, section 5.3.21 ISACA, CISA Review Manual, 27th Edition, chapter 5, section 5.42