To disable remote login
- Open the KDM configuration file for editing. 
Typically this file is located at /etc/X11/xdm/xdm-config or /usr/share/config/kdm/kdmrc on Redhat.
 - Look for the [XDMCP] section and verify that the Enable property is either not present, commented out, or is set to false, like this: 
[XDMCP] Enable=false.