Each object has a security attribute that identifies its access control list.
The list has an entry for each system user with access privileges.
The most common privileges include the ability to read a file (or all the files in a directory), to write to the file or files, and to execute the file (if it is an executable file, or program). Microsoft Windows NT/2000, Novell's NetWare, Digital's OpenVMS, and UNIX-based systems are among the operating systems that use access control lists.
The list is implemented differently by each operating system.
In Windows NT/2000, an access control list (ACL) is associated with each system object.
Each ACL has one or more access control entries (ACEs) consisting of the name of a user or group of users. The user can also be a role name, such as "programmer", or "tester".
For each of these users, groups, or roles, the access privileges are stated in a string of bits called an access mask. Generally, the system administrator or the object owner creates the access control list for an object.
