On 8/4/05, Thomas Sprinzing <thomas at sprinzing dot org> wrote:
> 
> is there any interest, idea, plan to implement port triggering in m0n0wall?
> 

the technical name for such a thing is uPNP.  I've explained why it's
worthless and dangerous on the pfsense list in the following thread,
so I won't repeat myself here.
http://www.mail-archive.com/support%40pfsense.com/msg00125.html

One reply:
http://www.mail-archive.com/support%40pfsense.com/msg00127.html

One comment on that reply, I'd say it's a huge risk in any
environment, not just corporate.  Think worms, viruses, trojans, and
other malware that could open a port in your firewall so outside
attackers could talk directly to whatever junk is on your machine(s).

-Chris