[TriLUG] looking for linux solution similar to openbsd's authpf

[Alan Porter]

> here's the desired outcome ... by default, iptables on server X blocks access to port Y. i successfully login to server X via ssh, and iptables gets updated to allow me (my ip) to pass through on port Y.

Take a look at knockd/knock.  A simple port-knocking daemon might be 
just what you're looking for.

If it's the SSH service that you're trying to hide, you can add the 
client knocking sequence to every SSH connection attempt by adding a 
line to $HOME/.ssh/config.

Alan