login using xwindows

Is there a way to find out who is logged in to the system using Xwindows ( hummingbird)..
I tried using
finger
and last
it doesn't show the person logged in ..
but when i run ps -ef | grep "ip address' it show various process running on the system..
Moreover is there a way to log off the person from the server.
I am trying to control the person logging in on the server and only trusted users can log in with their user id and password.
As of now system has only common userid and password.

Thanks in advance

I use a script which i programed to Kill the user and his session which doesnt have any authorisation to access in the machine. I have 5 NIS Main frame servers & 3 File Servers which i dont have time to Administer for who accessing and doing things in a place. The best possible way is to restrict the access thru running script act as a daemon on the client side.

You can try the below link look for AutoLog

The functions are similiar, which i think might get what you are looking for.

type: who

in Xwindow open a terminal & type "who" to see who is logged in.