how to disable some AD user can't login to server desk ?

how to disable some AD user can't login to server desk ?

Hi all,
   In my company, the is a specific department that need to deploy a server desk for all this dept users,  but other department users need not to login,and all the users are in a AD server, so, how do I specific only that dept user to login and disable other users  ?(also we can change the port, but this not a good choice, furthermore, I delete the import user from AD, but this user can also login)

                  New to ADSelfService Plus?