An introduction to IPTables and Firewalld in Linux

CentOS has an extremely powerful firewall built in, commonly referred to as iptables, but more accurately is iptables/netfilter. Iptables is the userspace module, the bit that you, the user, interact with at the command line to enter firewall rules into predefined tables. Netfilter is a kernel module, built into the kernel, that actually does the filtering. There are many GUI front ends for iptables that allow users to add or define rules based on a point and click user interface, but these often lack the flexibility of using the command line interface and limit the users understanding of what's really happening. We're going to learn the command line interface of iptables.

In this course you will be introduced to the iptables concept and will gain enough knowledge to go further into the field of OS security. I have chosen CentOS as the OS flavor which is the free version of Redhat. Since it is the most commonly deployed Linux flavor, you will be in a good shape to put your newly learned skills to test right away.

Although it will be good idea to some background on Linux for this course, but if you don't have it, don't worry about it. I will go over some basics at the beginning of the course.