Isn´t this more typical a task for the host you run sab on?
Iptables
Access control list for remote access
Re: Access control list for remote access
I've configured sabnzbd on my (linux) server to only listen to localhost / 127.0.0.1. To remotely connect to my sabnzbd interface, I simply open a SSH session to my server with a tunnel at port 8080. Maybe this would be a solution for you too?