VMS acquired this circa 1995, via a mechanism called protected subsystems, and specifically via a subsystem ACL. The associated access control list entry added

VMS acquired this circa 1995, via a mechanism called protected subsystems, and specifically via a subsystem ACL. The associated access control list entry added additional access onto the running program, and the rights were stripped off at exit. http://h71000.www7.hp.com/doc/73final/6346/6346pro_030.html http://h71000.www7.hp.com/doc/73final/6346/6346pro_030.html tl;dr of that web page: an administrative user can configure running programs to have their own identities granted via an access control list entry; identities which where then considered in conjunction with the user's identities.