Example netfilter setup contains a simple example on how to setup netfilter.
Warning this is experimental, I don't garantee this is 100% secure, it just does the work fine for me and i thought it could be a good jumpstart for people new to netfilter.
Now I am waiting for your corrections, suggestions and critics. Also I am gonna write a small addon for setting up dynamic rules cause i am tired of all these programs with dynamics port like bind, xdm and rpc.
Btw nmap -sU will still report udp dropping port as open.
nmap -sU -p 111 192.168.1.1