iptables - Config example

#!/bin/bash

###### SETUP ######

# VARS #

fw="iptables"

# Cleaning #

$fw -F
$fw -X
$fw -t nat -F
$fw -t nat -X
$fw -t mangle -F
$fw -t mangle -X

# Default Policy #

$fw -P INPUT DROP
$fw -P FORWARD DROP
$fw -P OUTPUT DROP

# Loopback interface #

$fw -A INPUT -i lo -j ACCEPT
$fw -A OUTPUT -o lo -j ACCEPT

###### CONFIG ######

# Sessions #

$fw -A INPUT -p all -m state --state ESTABLISHED,RELATED -j ACCEPT
$fw -A OUTPUT -p all -m state --state ESTABLISHED,RELATED -j ACCEPT

# SERVICES #

# All outgoing connections #

#$fw -A OUTPUT -p all -j ACCEPT

# SSH #

$fw -A INPUT -p tcp --dport 22 -j ACCEPT

####### LOG #######

# All undefined packets to new chain "undef_" #

$fw -N undef_in
$fw -N undef_out
$fw -N undef_fw
$fw -A INPUT -j undef_in
$fw -A OUTPUT -j undef_out
$fw -A FORWARD -j undef_fw

# Log all packages in chains undef_ #


$fw -A undef_in -j LOG --log-level 7 --log-prefix "Iptables: drop input: "
$fw -A undef_in -j DROP
$fw -A undef_out -j LOG --log-level 7 --log-prefix "Iptables: drop output: "
$fw -A undef_out -j DROP
$fw -A undef_fw -j LOG --log-level 7 --log-prefix "Iptables: drop forward: "
$fw -A undef_fw -j DROP

###### Save all rules ######

/sbin/service iptables save