I guess you mean KDM - the login manager, which is different than KDE (you can run them independently, anyway)
if you look in the kde control panel app, iirc there is a section for login manager, where you can set who can/cannot log in via KDM. you may also set access by searching for and editing a file called .kdmrc - location will vary per distro.
EDIT: you didn't specify which you're using, but there are at least two other login managers: GDM and XDM. I'm assuming they each have access lists, but I'm not familiar with them.
Last edited by Genesee; 09-10-2004 at 02:07 PM.