What's the easiest way to restrict access to a specific port on Ubuntu?

i have heard iptables is the way to go…. i’ll see if i can’t find some resources….

http://iptables-tutorial.frozentux.net/iptables-tutorial.html

looks to be a pretty long resource, if you need more help, let me know….

Iptables is exactly what you want:

https://help.ubuntu.com/community/IptablesHowTo

something like this:

# allow access to that port only from specific IP addresses
sudo iptables -A INPUT -p tcp—dport YOUR_PORT_NUMBER -d IPADDRESS1 -j ACCEPT
sudo iptables -A INPUT -p tcp—dport YOUR_PORT_NUMBER -d IPADDRESS2 -j ACCEPT

etc.

# by default for everyone else, block all access to that port
sudo iptables -A INPUT -p tcp—dport YOUR_PORT_NUMBER -j REJECT

note if the IP address are contiguous, you can specify a mask along with the ipaddress. For example, 192.168.0.1/30 will match 192.168.0.0 – 192.168.0.3.

be sure to read the section on “Configuration on startup” in the above link, as iptables does not load automatically on startup or reboot.

Ubuntu 8.04 has a new application called “uwf” (uncomplicated firewall) which is supposed to be a lot easier to setup. I haven’t tried it myself though (I prefer using graphical applications but even then I have no idea what to do in Firestarter).