fw.sh

#!/bin/bash

# RESET RULES
iptables -F INPUT
iptables -F OUTPUT
iptables -F FORWARD
iptables -t nat -F
iptables -F
iptables -X
iptables -Z

# DEFAULT POLICY
iptables -P FORWARD DROP
iptables -P INPUT DROP
iptables -P OUTPUT DROP

# Enable only for a router
#iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

# MISC - Allow established connections
iptables -A FORWARD -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT

# MISC - Allow ping
iptables -A INPUT -p icmp -j ACCEPT
iptables -A OUTPUT -p icmp -j ACCEPT

# Uncomment only when above rules are tested and valid
#iptables-save