The old UNIX file permission system is commonly the only method of access control that people use. The basic file ownership permissions (user, group, and world/other) on UNIX are a bit outdated.

Unix systems use UFS, ext2, ext3 and ZFS. See journaling file system, hierarchical file system, block level, cluster, FAT32, NTFS, APFS, HFS, NFS, UFS, ext and ZFS.