# Flush all entries
iptables -F

# Allow connections through loopback device
iptables -A INPUT -i lo -p all -j ACCEPT
iptables -A OUTPUT -o lo -p all -j ACCEPT

# Allow incoming connection if they're related or established
iptables -A INPUT -i eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT

# Drop everything else.
iptables -P INPUT DROP
iptables -P FORWARD DROP