What is an access control list (ACL)?

An access control list (ACL) is fundamentally a set of rules that specifies which users or system processes are granted access to objects and what operations are allowed on given resources within a network. This can include permissions such as read, write, execute, and delete for files, directories, and network assets.

ACLs are critical for enforcing security policies in various computing environments, enabling administrators to specify access controls based on user roles, ensuring that only authorized individuals can interact with sensitive data or critical systems. This serves to protect resources from unauthorized access and helps in maintaining the overall security posture of an organization.

The other options describe different concepts that do not relate to the functionality of an ACL. Private user data refers to information owned by users and does not encompass the rules or permissions that regulate access to resources. A backup system pertains to solutions for preserving data in case of loss, which is unrelated to access management. Meanwhile, methods for encrypting sensitive information focus on protecting data from unauthorized views rather than managing access rights or permissions.