you need iptables (Kernel 2.4)

See firewall-book for kernel settings or: * http://www.netfilter.org/unreliable-guides/packet-filtering-HOWTO/packet-filtering-HOWTO.linuxdoc.html * http://www.linuxvoodoo.com/howto/iptables/iptables-tutorial.html

A very simple firewall is firestarter available at http://firestarter.sourceforge.net/

It has wizard to configure a firewall. Install package firestarter.

You may also use IpMasq.

To analyze log messages use FwLogWatch.

see also: * package fwbuilder * package easyfw * package firewall-easy

firewall-easy

Maybe the debian package is incomplete or it only supports ipchains.

Some more docs

Documentation abounds on firewalling, from a quick Google I got

and of course, if you want bleeding edge (2.4 kernels)