When I first touched linux, I installed Zorin. It's essentially an Ubuntu fork, but the desktop is redesigned to make it look like home to a person who has been using Windows for a long time. It came with a firewall pre-installed. A few months ago I decided that some answers to questions here were pretty incompatible with Zorin (especially using the dash, as it does not exist there). The installation was also generally pretty broken.
I just noticed that Ubuntu doesn't seem to come with a firewall pre-installed. I am, unlike this one, pretty much a geek and I will likely have not much trouble setting it up. My question is, is it a better idea to install that firewall for this system, or leave it alone? Because it seems to not come with a firewall, but maybe there's one running in the background, where I cannot see it.
This question is also not exactly a duplicate of this one, that one doesn't know if they need one, I already know I need one, but I am not sure if I need to install one or if there's already one running in the background.