Iptables
Introduction
Iptables is a powerful firewall tool that is used to manage and secure traffic that passes in and out of a Linux-based system. It is a fundamental component of any Linux system, and it is essential for system administrators to understand how iptables works and how to use it effectively.
Reference
https://www.booleanworld.com/depth-guide-iptables-linux-firewall/
https://man7.org/linux/man-pages/man8/iptables.8.html
https://www.netfilter.org/projects/iptables/index.html
https://mdsh.com/wiki/jsp/Wiki?topic=iptables&action=action_printable