Explanation
Change control is the process of ensuring that changes to an information system are authorized, tested, documented and implemented in a controlled manner. Inadequate change control can result in deficient technical security controls, such as missing patches, misconfigurations, vulnerabilities or errors in the new application.
References = CISM Review Manual, 27th Edition, Chapter 4, Section 4.3.2, page 2291

Business process owners are in the best position to understand how new regulatory requirements may affect their systems. Legal counsel and infrastructure management, as well as internal auditors, would not be in as good a position to fully understand all ramifications.

Explanation
Security' code reviews for the entire application is the best measure and will involve reviewing the entire source code to detect all instances of back doors. System monitoring for traffic on network ports would not be able to detect all instances of back doors and is time consuming and would take a lot of effort. Reverse engineering the application binaries may not provide any definite clues. Back doors will not surface by running the application on high-privileged accounts since back doors are usually hidden accounts in the applications.

Explanation/Reference:
Explanation:
Mandatory access controls restrict access to files based on the security classification of the file. This prevents users from sharing files with unauthorized users. Role-based access controls grant access according to the role assigned to a user; they do not prohibit file sharing. Discretionary and lattice-based access controls are not as effective as mandatory access controls in preventing file sharing. A walled garden is an environment that controls a user's access to web content and services. In effect, the walled garden directs the user's navigation within particular areas, and does not necessarily prevent sharing of other material.