19.1. Introduction to Firewalling with IPtables

A firewall is a system that protects itself and other hosts on a network from attackers on untrusted networks, such as the Internet. It can block packets and connections based on a variety of criteria, such as the source address, destination address, port, and protocol. Typically a firewall is also a router, forwarding packets between a secure local network and the untrusted Internet—however, it is also possible for a system to protect just itself.

A firewall system can also be configured to hide multiple hosts behind a single IP address, using a process known as NAT (Network Address Translation). Typically, the hidden hosts are on an internal LAN using a private IP network (such as 192.168.0.0) ...

Get Managing Linux® Systems with Webmin™ System Administration and Module Development now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.