Every directory has its own ACL that defines who can access the directory and its files. Each ACL may define as many as 20 users and groups.
Groups are lists of users.
Some groups are created by the system, but users can also create their own groups. See the CPC document AFS Protection Groups for more details about protection groups. Individual file protection is based on the rights granted by the ACL for the file's directory combined with the Unix 'owner rwx' bits. For further details, see the section below, Using the UNIX Mode Bits in AFS . There are seven access rights available on ACLs.