These additional system-generated users are automatically created at system startup.
Most system-generated users perform important system-level functions. Do not alter the database privileges for any system user unless the documentation or Teradata Support personnel specifically direct you to do so. You should limit access to system-generated users to trusted administrators.
An exceptions to this rule are EXTUSER, PUBLIC, and SYS_CALENDAR, which you can administer according to site policy.
For more information on system-generated users, see Teradata Vantage™ - Database Administration, B035-1093.