Harrison, Ruzzo, Ullman (HRU)
This model is very similar to the Graham-Denning model and composes a set of generic rights and a finite set of commands. It is also concerned with situations in which a subject should be restricted from gaining particular privileges.
4 slides · 1 min read · Domain 3
To do so, subjects are prevented from accessing programs, or subroutines, that can execute a particular command (to grant read-access for example) where necessary.
Modern Implementation
Most modern operating systems implement elements of these security models. They are not perfect implementations of the academic models and focus on practical implementations that provide functionality consistent with one or more of the security models.