6.1. Firewalls

• The transport layer is the main layer for firewalls to operate in.
• The main function of firewalls is to filter the packets transferred on the network, so that only the packets we wish to accept will come through.
• There are two types of firewalls: stateful and stateless.
• The Linux Kernel has a built-in stateful firewall module, called "iptables" or "netfilter".
• More details about configuring firewall in Linux can be found here: http://www.netfilter.org/documentation/index.html#HOWTO
• Eli Billauer has given a lecture about iptables.

Written by Shlomi Fish