Basic iptables firewall (CentOS 6)

setup_iptables.sh

#!/bin/bash

# Flush all current rules from iptables
iptables -F
ip6tables -F

# Allow SSH connections on the following tcp ports
iptables -A INPUT -p tcp --dport 22 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp --dport 110 -j ACCEPT
iptables -A INPUT -p tcp --dport 143 -j ACCEPT
iptables -A INPUT -p tcp --dport 993 -j ACCEPT
iptables -A INPUT -p tcp --dport 995 -j ACCEPT
iptables -A INPUT -p tcp --dport 3306 -j ACCEPT
ip6tables -A INPUT -p tcp --dport 22 -j ACCEPT
ip6tables -A INPUT -p tcp --dport 80 -j ACCEPT
ip6tables -A INPUT -p tcp --dport 110 -j ACCEPT
ip6tables -A INPUT -p tcp --dport 143 -j ACCEPT
ip6tables -A INPUT -p tcp --dport 993 -j ACCEPT
ip6tables -A INPUT -p tcp --dport 995 -j ACCEPT
ip6tables -A INPUT -p tcp --dport 3306 -j ACCEPT

# Set default policies for INPUT, FORWARD and OUTPUT chains
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT ACCEPT
ip6tables -P INPUT DROP
ip6tables -P FORWARD DROP
ip6tables -P OUTPUT ACCEPT

# Set access for localhost
iptables -A INPUT -i lo -j ACCEPT
ip6tables -A INPUT -i lo -j ACCEPT

# Accept packets belonging to established and related connections
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
ip6tables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# Save settings
/sbin/service iptables save
/sbin/service ip6tables save

# List rules
iptables -L -v
ip6tables -L -v