Overview of firewall configuration
When a system is connected to a network, many of the services running can be reached from other systems. That is the goal behind having systems connected. However, we also want to keep systems secure and away from unauthorized usage.
A firewall is a software layer that sits between the network cards and the services and allows us to fine-tune what is allowed or not.
We cannot completely block all the incoming connections to our system as often, the incoming connection is a response from a request that our system made.
The connections are blocked via a kernel framework named netfilter, which is used by the firewall software to modify how the packets are processed. Nftables is a new filter and packet classifier subsystem that enhances parts of netfilter code, but retains the architecture and provides faster processing among other features using only one interface (nft), thus deprecating old frameworks such as iptables, ip6tables, ebtables,...