Explanation
Reviewing input and output control reports to verify the accuracy of the system decisions is the most important procedure for the IS auditor to perform during the post-implementation review of intelligent-agent software for granting loans to customers, because it can help identify any errors or anomalies in the system logic or data that may affect the quality and reliability of the system outcomes. Reviewing system and error logs, signed approvals, and system documentation are also important procedures, but they are not as critical as verifying the accuracy of the system decisions. References: CISA Review Manual (Digital Version), Chapter 4, Section
4.2.21

Explanation
The IS auditor's independence would be most likely impaired if they implemented a specific control during the development of an application system. This is because the IS auditor would be auditing their own work, which creates a self-review threat that could compromise their objectivity and impartiality. The IS auditor should avoid participating in any operational or management activities that could affect their ability to perform an unbiased audit. The other options do not pose a significant threat to the IS auditor's independence, as long as they follow the ethical standards and guidelines of the profession.

A call-back system in a net centric environment would mean that a user with an id and password calls a remote server through a dial-up line first, and then the server disconnects and dials back to the user machine based on the user id and password using a telephone number from its database. Although the server can depend upon its own database, it cannot know the authenticity of the dialer when the user dials again. The server cannot depend upon the sender's database to dial back as the same could be manipulated.

Explanation/Reference:
Application-layer gateways, or proxy firewalls, are an effective method for controlling downloading of files via FTP. Because FTP is an OSI application-layer protocol, the most effective firewall needs to be capable of inspecting through the application layer.