Basic iptables rules for web server

rules.sh

#!/bin/bash

# flush all chains
iptables -F
iptables -X

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

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

# allow traffic once a connection has been made
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT

# syn flod protection
iptables -N SYN_FLOOD
iptables -A INPUT -p tcp --syn -j SYN_FLOOD
iptables -A SYN_FLOOD -m limit --limit 5/s --limit-burst 10 -j RETURN
iptables -A SYN_FLOOD -j DROP

# accept anything on ssh port
iptables -A INPUT -p tcp --dport ssh -j ACCEPT

# accept anything on glink port
iptables -A INPUT -p tcp --dport 80 -j ACCEPT