A list of security protections that applies to an object. (An object can be a file, process, event, or anything else having a security descriptor.) An entry in an access-control list (ACL) is an access-control entry (ACE). There are two types of access-control list: discretionary and system. See also access-control entry (ACE), discretionary access-control list (DACL), security descriptor, system access-control list (SACL).