Prev Chapter 5. Generic Network Configuration Information. Network Security and access control. Let me start this section by warning you that securing your machine and network against malicious attack is a complex art. I do not consider myself an expert in this field at all and while the following mechanisms I describe will help, if you are serious about security then I recommend you do some research of your own into the subject.
Many distributions come configured with all sorts of services configured and automatically started.
There are all sorts of security and access control mechanisms, I'll describe the most elementary of them. The file is a simple list of those users who are disallowed from logging in. The tcpd hosts access control mechanism. When it is invoked by the inetd program it reads two files containing access rules and either allows or denies access to the server it is protecting accordingly. It will search the rules files until the first match is found.