Simple Iptables Shell Script

All Scripts written under Ubuntu 7.04

#!/bin/bashipt=/sbin/iptables
# flush all chains$ipt -F

$ipt -X
$ipt -Z

# set the default policy for each of the pre-defined chains
$ipt -P INPUT DROP
$ipt -P OUTPUT DROP
$ipt -P FORWARD DROP

# accept anything on loopback
$ipt -A OUTPUT -d 127.0.0.1 -o lo -j ACCEPT
$ipt -A INPUT -s 127.0.0.1 -i lo -j ACCEPT

# to allow incoming/outgoing DNS
$ipt -A INPUT -p udp --sport 53 -j ACCEPT
$ipt -A OUTPUT -p udp --dport 53 -j ACCEPT

# Let established traffic origin from local system pass thru

#tcp
$ipt -A INPUT -p tcp -i eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT
$ipt -A OUTPUT -p tcp -o eth1 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT

#udp
$ipt -A INPUT -p udp -i eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT
$ipt -A OUTPUT -p udp -o eth1 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT

#icmp
$ipt -A INPUT -p icmp -i eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT
$ipt -A OUTPUT -p icmp -o eth1 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT

~ by aric on July 28, 2007.