A small amount of descriptive data (meta-data) that is added to a computer file by the user or network administrator. It is maintained by the file system but is not part of the file's regular set of attributes (see file attribute). A feature of Linux and Unix operating systems, access control lists, which define the permissions for the file, are often stored as extended file attributes. System Attributes Extended file attributes are assigned categories, and the "system" category is typically used to hold access control lists. For example, Linux defines "system," "user," "trusted" and "security" attributes. In the Mac OS X operating system, users have the option of storing comments with a file. As of Version 10.5, these "Spotlight Comments" are stored as extended file attributes and can be viewed in Finder and searched in Spotlight. See access control list.