I am making a move to Linux from Windows as my primary PC for being on-line. I really liked Comodo's Personal Firewall on Windows where I was given a chance to learn what software on my machine was trying to connect to the internet. Also, it was my understanding that Comodo took extra steps to make sure that software could not trick it's way past the firewall by invoking other processes to mask it's EXE such as Internet Explorer or Run.dll. On Ubuntu MATE 16.04 I have gufw protecting against all inbound traffic which I believe is a bit redundant given that Ubuntu apparently has all ports closed by defaults. Outbound traffic, however, is wide open unless I choose to turn it off completely. And at that point I might as well unplug my ethernet cable. So I would like Firefox (running in firejail) and Ubuntu update\software services to be able to get out, but I would like to start checking everything else. For instance, I may wish to use a Jetbrains IDE product that requires license registration on purchase to talk to one of their servers, but after I register the product I don't need it continuing to phone home reporting my usage or whatever. Are there are any good open source options out there? Open source is obviously preferable to something like Comodo which may have hidden code phoning home. Hopefully not, but I may have placed too much trust in that company. Thanks in advance!