Lock down XDMCP?

[Romeyn Prescott]

I have a box at home that I want to sit headless...no 
monitor/keyboard/mouse.  I'll "use" it remotely from one of my other 
computers by logging in via ssh and running 'gdmflexiserver -n'. 
This works great.

How do I lock down XDMCP so that commands like 'X :1 -query 
ip.address.of.box' don't work?  It's not terribly secure.

Thanks,
...ROMeyn
-- 
signat-url: http://www2.potsdam.edu/prescor/signat-url.htm