Also sometimes known as a system group, a special group account on a computer running Microsoft Windows NT or Windows 2000 that you can use to control security and access to NTFS volumes.
Special identities are groups whose membership is controlled by the operating system itself, not by administrators or individual users. User accounts become “members” of these special groups based on the type of system activity they participate in; you cannot modify the “membership” of these groups directly.
Special identities on Windows NT systems include the following:
Additional special identities in Windows 2000 include the following: