I ran into a problem with a client running an IPFire firewall, where they had employees using teamviewer.com to access their workstations after hours, effectively bypassing the security of the router.
I came up with a solution. Possibly not the best one as it requires building a separate name server, but it at least works. I wrote a "How To" on one of my sites, but if you think it would be useful, let me know where I should put it.
http://wiki.linuxservertech.com/index.php?action=artikel&cat=5&id=19...
Feel free to tell me there are better ways to do it or there are better uses of the web site.
Rod