Final answer:
To prevent a visitor from picking up a CD from an employee's desk, physical access controls, audit controls, and data encryption should have been implemented to ensure only authorized access, track the movement within the area, and safeguard the data on the CD.
Step-by-step explanation:
To prevent the security breach where a visitor picked up a CD from an employee's desk, several security controls should have been implemented. The most relevant among them are physical access controls, which would ensure only authorized personnel can enter certain areas of the department. Additionally, audit controls are crucial as they would track and log access to the department, potentially deterring theft and aiding in the investigation post-incident. Although not directly related to the physical theft of a CD, data encryption is a security measure that protects the confidentiality of the data stored on the CD, in case it is misplaced or stolen. However, it is important to mention that in this scenario, biometric access control is not mentioned as a necessary control as it falls under the broader category of physical access controls.