Comment 4 for bug 544976

Anyone connecting to the internet via a router or wireless router must configure the device to ignore (not respond to) ping, ICMP or whatever the device calls this setting.

From my understanding, having the firewall in Ubuntu AND a firewall in the router/wireless router offers the best security. You cannot install more than one firewall on the computer itself in the same operating system - it is not a good idea to even try that!

If you don't have a router/wireless router then the firewall in Ubuntu MUST be properly configured to make your computer invisible on the internet and stop hackers from being able to get in. I don't know the technical stuff beyond what I've typed in this message.