IpTablesConfig

iptables.sh

#!/bin/bash

iptables -F
# Defautlt policy
iptables -P INPUT DROP
iptables -P OUTPUT ACCEPT
iptables -P FORWARD DROP

# drop invalid packets
iptables -A INPUT -m state --state INVALID -j DROP

# see http://www.faqs.org/docs/iptables/newnotsyn.html
iptables -A INPUT -p tcp ! --syn -m state --state NEW -j DROP

# accept anything on localhost
iptables -A INPUT -i lo -j ACCEPT

# accept ICMP packets
iptables -A INPUT -p icmp -j ACCEPT

# allow specific ports
iptables -A INPUT -p tcp -s 0/0 --dport 22 -j ACCEPT
iptables -A INPUT -p tcp -s 0/0 --dport 80 -j ACCEPT
iptables -A INPUT -p tcp -s 0/0 --dport 443 -j ACCEPT

# allow establishment of connections initialised by my outgoing packets
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT