Question: Which of the following statements regarding operating system security mechanisms is correct?

A) The principle of least privilege states that users should have the minimum level of access necessary to perform their tasks, which helps reduce the risk of accidental or malicious damage.
B) Encryption of data at rest ensures that data is secure only while it is being transmitted over a network but does not protect it when stored on disk.
C) Access control lists (ACLs) can only be applied to files and directories but not to network resources or devices.
D) A firewall is primarily designed to prevent unauthorized access to a system by monitoring and controlling incoming and outgoing network traffic based on predetermined security rules.