What is an access control list (ACL)?

An access control list (ACL) is defined as a set of rules that determines who can access certain resources in a computer system. This definition highlights the core function of an ACL, which is to manage permissions and specify which users or system processes are granted or denied access to particular system objects, such as files, directories, or network devices. By using an ACL, administrators can enforce policies regarding user access, ensuring that only authorized individuals can interact with sensitive information or perform specific actions within the system.

The importance of ACLs lies in their ability to enhance security by providing fine-grained access control. They are crucial in environments where data protection and compliance with regulations require strict access management. This supports overall security governance and helps in safeguarding information assets.

In contrast, the other options focus on different concepts not directly related to the function of an ACL. Logging user access attempts pertains to tracking and monitoring activities but does not dictate access permissions. A protocol for securing data transmissions relates to communication security rather than resource access control. A physical barrier is a tangible security measure that does not address access constraints in a digital context. These distinctions clarify why the definition of an ACL as a set of access control rules is the most accurate and relevant choice.