The Enemy Within: Firewalls and Backdoors
hrbrmstr writes "SecurityFocus is running an article on firewalls and backdoors on their InFocus site. They provide info on firewall types, backdoor classifications, some examples of real backdoors and tips on mitigating their use on your network." Some good topics explained for the beginner, and it's a nice refresher for the veteran admin as well.
security through obscrurity does not work
it is only after a long journey that you know the strength of the horse.