Port knocking: a stealthy system for network authentication across closed ports

Firewall Primer

Perl prototype: v0.30

pcaplib support added; daemon no longer requires firewall log file

2004-Nov-14 18:59 | ...more

new Net::Pcap support added to sniff packets directly ...more

This section introduces the idea of communication ports and firewalls at a very introductory level. If you are familiar with TCP/IP and firewalls, you can skip past this section and go straight to the details of the port knocking implementation. This introduction is not a technical document and is targetted at a non-technical audience or novices computer users and administrators.

ports packets services allocation firewalls rationale ip filtering limitations resources

You can find more details in the Linux Firewall HOWTO by Rusty Russell. The section on packet filtering basics is particularly readable for beginners. For a broader description of firewalls, see the Linux Firewall HOW-TO by Mark Grennan. Mark points out the difference between filtering, proxy, application proxy and SOCKS proxy firewalls.

last updated 2003-Jul-18 16:21