Behold the words of the ubuntu fanboi!
As for firewall, I can recommend and do support
ipmasq. Although it doesn't have a gui like other packages, it also stays out of your way and sets up a tight firewall. I have used this package for many years; I also tried out other firewall packages but always came back to ipmasq.
And while I am going on about
-masq, let me tell you about
dnsmasq, which is a simple and very reliable dhcp server and caching dns server.
To make the sugar even sweeter (and I cannot resist doing so), I have to direct your attention to yet another package, this time it's a little helper tool called
resolvconf. resolvconf makes ipmasq and dnsmasq work nicely together; it's the grease between these two 1338 packages.
Now, I admit, 3 packages at once might be a little difficult, but: they work so nicely together it definitely is worth the effort of getting to know them. Also, I am willing to help you setting them up (this is an easy promise, they don't need much setting up
)