No Need To Secure Server

I have a friend that works in the IT. He is about to start his own business, something in the line of network connection or something like that. I was telling him that I'm planning on getting my own dedicated server but that I have no idea how to secure the server. He told me that most linux desitributions come with their own build in firewall and that I don't need to worry about security. He told me to just ask my dedicated server provider to make sure the firewall is enabled and that's it. When he told me that I thought to myself, either this guy has no idea what he's talking about, or those guys at Webhostingtalk have no idea what they are talking about!