In using a Linux OS instead of Windows, many pieces of Malware will not be applicable to the Linux operating system and ineffective. A bit how a virus that targets newts will not have any affect on a human.
I agree with all comments about the firewall: Set it up as Default. Denying connections manually is more likely to cause you headaches. I understand if you want to learn more- that will take time and a forum is not really the ideal place to get a thorough education. A forum is good for fast tips and help. During the time that you spend learning more and more about firewall configuration, through documentation, you can rely on the default firewall settings to keep you in the clear.
Even so, there is only so much you can do with a firewall. Think First Party, Second Party, Third party. Let's say that you want to buy a watch.
First Party is if you go to a reputable watch dealer.
Second party is if a friend offers to buy you the watch, as he says he 'knows a guy', and he then provides the watch to you.
Third party is if that friend has an agent, that buys the watch from some source, provides it to the friend, he then provides it to you.
Clearly, you can see that the safest option above is the First Party. Visiting a website or reading an email is the same.
It is best to avoid clicking links provided in an email as often as possible. Some sites use email verification with a link. You can check the sources before clicking it, however. But any link provided in an email that You Did Not Request is suspect.
While computers and programs can be impressive in how their algorithms work, they are still nowhere near to Human Intelligence, reasoning and decision making. You are the most powerful and intelligent firewall available to your computer. You can make fast decisions, double check a source, search the source rather than clicking a second party link and so on. A firewall cannot do any of that - it can only block regardless of content.
