redhat-config-securitylevel & lokkit

[Logan]

I would recommend to:

    - google for some firewall examples using iptables
    - have 'man iptables' at hand
    - write your own firewall (no joke!)

Otherwise, you will never know, what your firewall is
really doing. 

(iptables look a little bit confusing in the beginning; but there are
many examples for firewalls on the web which help a lot in the
beginning; you can just build your own firewall by extending resp.
modifying an existing example.)