What is used to restrict a user's or group's ability to read, write, and execute files in an operating system?

• A. Access Control Lists (ACL)
• B. Authentication
• C. Secure passwords
• D. Multi-factor authentication

Answer: (A)

Access control lists provide the specific permissions that govern what actions a user or group can take on a file or directory. They attach entries to a resource that grant or deny read, write, and execute rights to particular users or groups, giving fine-grained control over who can do what. This is how an OS enforces who can view, modify, or run a file once a user has been identified. Authentication methods like passwords or multi-factor authentication are about verifying identity, not about specifying what actions are allowed after access is granted. So restricting read, write, and execute privileges on files is achieved through Access Control Lists.