#!/bin/bash
IPT="/sbin/iptables"
modprobe ip_tables
$IPT -F
$IPT -F -t nat
$IPT -X firewall
 
#Set up the firewall chain
$IPT -N firewall
$IPT -A firewall -j LOG --log-level info --log-prefix "Firewall:"
$IPT -A firewall -j DROP
 
#Accept ourselves
$IPT -A INPUT -s 127.0.0.1/32 -d 127.0.0.1/32 -j ACCEPT
 
#Accept SSH.  
#$IPT -A INPUT -p tcp --destination-port 22  -j ACCEPT
 
#Send everything else ot the firewall.
$IPT -A INPUT -p icmp -j firewall
$IPT -A INPUT -p tcp --syn -j firewall
$IPT -A INPUT -p udp -j firewall
 

#!/bin/bash
 
######################################################
#First, we flush everything to avoid duplicate chains#
######################################################
 
#
# reset the default policies in the filter table.
#
iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT
 
#
# reset the default policies in the nat table.
#
iptables -t nat -P PREROUTING ACCEPT
iptables -t nat -P POSTROUTING ACCEPT
iptables -t nat -P OUTPUT ACCEPT
 
#
# flush all the rules in the filter and nat tables.
#
iptables -F
iptables -t nat -F
 
#
# erase all chains that's not default in filter and nat table.
#
iptables -X
iptables -t nat -X
 
#########################Firewall Begin####################
 
###########################
#Disable response to ping.#
###########################
/bin/echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_all  
 
################################
#Disable response to broadcast.#
################################
/bin/echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts  
 
######################
#Set Default Policies#
######################
 
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD ACCEPT
 
#####################################################
# Allow unlimited traffic on the loopback interface.#
#####################################################
iptables -A INPUT  -i lo -j ACCEPT  
iptables -A OUTPUT -o lo -j ACCEPT  
 
 
#############################
# Local Net Network Rules #
#############################
iptables -A INPUT -i eth0 --protocol tcp --source-port 22 -m state --state ESTABLISHED
iptables -A OUTPUT -o eth0 --protocol tcp --destination-port 22 -m state --state NEW,ESTABLISHED