After Voids request, lets make this the central thread about iptables,
Just to give an idea to the other members, I asked in the RedHatd ( http://voidmain.is-a-geek.net/forums/viewtopic.php?t=89 about how to close the famous port 6000.
Voidam trying to close port 6000............ I run netstat -lp and I dont see any port 6000 open. ............... did a port scan with my other machine to the above machine yet the port is still open.
I usually use "iptables" to block all that sort of stuff (firewall). Or block it from everywhere except from specific client addresses. are you really using XDM or are you using KDM or GDM to start an X session? If you are using GDM then I would say you need to add the parameter to /etc/X11/gdm/gdm.conf (or one of the other configuration files under that directory. If you are using KDM you might want to look through the /etc/X11/xdm/kdmrc file and see if it spawns X from another location. Regardless, iptables is the easiest way and independent of which X display manager you use. For servers that touch the Internet I do a mostly closed configuration. I deny everything on the outside interface except for the specific ports I want coming in. And then I restrict those ports to the specific IP addresses/ranges that need to connect to them. I also block a lot of outbound traffic in many cases so if a breach of one of the open services were to occur information may not be able to be sent back to the person doing the breaching.. ............. iptables really isn't that hard. In fact you can use the graphical Red Hat firewall utility or webmin to configure it if you want. They all use iptables and /etc/sysconfig/iptables save file. I prefer command line or webmin.