Anyone read these articles?  Any ideas how to implement with m0n0wall/IPFilter? It's an interesting
concept.

http://slashdot.org/article.pl?sid=04/02/05/1834228&mode=thread&tid=126&tid=172
http://www.linuxjournal.com/article.php?sid=6811&mode=thread&order=0
http://www.portknocking.org/