Reviewing the last compile date of production programs is the most efficient way to detect unauthorized changes to production programs, as it can quickly identify any discrepancies between the expected and actual dates of program modification. The last compile date is a timestamp that indicates when a program was last compiled or translated from source code to executable code. Any changes to the source code would require a recompilation, which would update the last compile date. The IS auditor can compare the last compile date of production programs with the authorized change requests and reports to verify that only approved changes were implemented. The other options are not as efficient as option A, as they are more time-consuming, labor- intensive or error-prone. Manually comparing code in production programs to controlled copies is a method of verifying that the code in production matches the code in a secure repository or library, but it requires access to both versions of code and a tool or technique to compare them line by line. Periodically running and reviewing test data against production programs is a method of verifying that the programs produce the expected outputs and results, but it requires designing, executing and evaluating test cases for each program.
Verifying user management approval of modifications is a method of verifying that the changes to production programs were authorized and documented, but it does not ensure that the changes were implemented correctly or accurately. References: CISA Review Manual (Digital Version) , Chapter 4: Information Systems Operations and Business Resilience, Section 4.3: Change Management Practices.

The greatest concern for an IS auditor in this scenario is that the user department will manage access rights to the new accounting system. This could pose a significant risk of unauthorized access, segregation of duties violations, data tampering and fraud. The IS auditor should ensure that access rights are defined, approved and monitored by an independent function, such as IT security or internal audit. The other options are not as concerning as option C, as they can be mitigated by other controls or procedures. Data migration is an important part of the system replacement project, but it can be performed by another party or verified by the IS auditor. The timing of the replacement near year-end reporting is a challenge, but it can be managed by proper planning, testing and contingency plans. Testing performed by the third-party consultant is acceptable, as long as it is reviewed and validated by the IS auditor or another independent party. References: CISA Review Manual (Digital Version) 1, Chapter 3: Information Systems Acquisition, Development & Implementation, Section 3.4: System Implementation.

Post-implementation testing is the process of verifying and validating the functionality, performance, and security of a system after it has been deployed to the production environment1. Post-implementation testing is important for ensuring that the system meets the user requirements and expectations, as well as the operational and business objectives. Post-implementation testing also helps to identify and resolve any defects, errors, or issues that may have occurred during the deployment process or that may have been missed during the previous testing stages2.
Therefore, the observation that post-implementation testing is not conducted for all system releases should be of greatest concern to an IS auditor performing an audit of change and release management controls for a new complex system developed by a small in-house IT team. This observation indicates that the system may have quality, reliability, or security problems that could affect the user satisfaction, system performance, or data integrity. This observation also suggests that the change and release management controls are not adequate or effective, as they do not ensure that all system releases are properly tested and validated before and after deployment.
Option A is not correct because access to change testing strategy and results is not restricted to staff outside the IT team is not a major concern for an IS auditor. While it is good practice to limit access to sensitive or confidential information, such as test data or test cases, to authorized personnel only, access to change testing strategy and results may not pose a significant risk to the system or the organization. Moreover, access to change testing strategy and results may be beneficial for some stakeholders outside the IT team, such as business users, project managers, or auditors, who may need to review or evaluate the testing process or outcomes.
Option B is not correct because some user acceptance testing (UAT) was completed by members of the IT team is not a major concern for an IS auditor. User acceptance testing is the process of verifying and validating that the system meets the user requirements and expectations by involving actual or representative users in the testing process3. While it is preferable to have independent and unbiased users perform UAT, it may not be feasible or practical for some organizations, especially those with small or limited resources.
Therefore, some UAT may be completed by members of the IT team, as long as they have sufficient knowledge and experience of the user needs and expectations, and as long as they follow the UAT plan and criteria.
Option C is not correct because IT administrators have access to the production and development environment is not a major concern for an IS auditor. IT administrators are responsible for managing and maintaining the IT infrastructure, including the production and development environments4. Therefore, it is reasonable and necessary for them to have access to both environments, as long as they follow the appropriate policies and procedures for accessing, using, and securing them. Moreover, IT administrators may need to perform tasks such as backup, restore, patching, or troubleshooting in both environments.
References:
What Is Post Implementation Testing?1
Post Implementation Review (PIR) - Definition & Process2
User Acceptance Testing (UAT): Definition & Examples3
What Is an IT Administrator? Definition & Examples4

Imaging the affected system is the best way to protect evidence in a forensic investigation, because it creates a bit-by-bit copy of the original data that can be analyzed without altering or compromising the original source. Imaging preserves the integrity and authenticity of the evidence and allows for verification and validation of the results34. Powering down or rebooting the affected system can cause data loss or corruption, while protecting the hardware does not prevent unauthorized access or tampering with the software or data. References: 3: CISA Review Manual (Digital Version), Chapter 6, Section 6.4.1 4: CISA Online Review Course, Module 6, Lesson 4