Firewall Facts

This document provides an overview of firewalls, including what they are (isolating an internal network from the internet), why they are used (to prevent attacks and unauthorized access), and the main types (packet filtering and application gateways). It also discusses limitations of firewalls and how they work in Linux using netfilter and iptables commands. Examples are given of common iptables rules to filter traffic, accept/reject connections, and drop packets.