In this section, we are going to set up a firewall using iptables. iptables is the standard firewall software present in most Linux distributions. We are going to use these set of rules to filter the network traffic. You can protect the server from unwanted traffic by filtering the data packets by specifying the source or destination IP address, port addresses, protocol types, network interfaces, and so on. We can configure this for accepting, rejecting, or forwarding network packets.

Rules are arranged in chains. By default, there are three chains (input, output, and forward). The input chain handles incoming traffic, while the output chain handles outgoing traffic. The forward chain handles routing traffic. Each chain has a default policy to adhere to if network packets do not match any policy inside the chain.