# Clear any existing firewall stuff before we start
iptables --flush
iptables -t nat --flush
iptables -t mangle --flush
# As the default policies, drop all incoming traffic but allow all
# outgoing traffic. This will allow us to make outgoing connections
# from any port, but will only allow incoming connections on the ports
# specified below.
iptables --policy INPUT DROP
iptables --policy OUTPUT ACCEPT
# Allow all incoming traffic if it is coming from the local loopback device
iptables -A INPUT -i lo -j ACCEPT
# Accept all incoming traffic associated with an established
# connection, or a "related" connection
iptables -A INPUT -i eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT
# Allow incoming connections
# SSH
iptables -A INPUT -p tcp -i eth0 --dport 22 -m state --state NEW -j ACCEPT
# HTTP
iptables -A INPUT -p tcp -i eth0 --dport 80 -m state --state NEW -j ACCEPT
# HTTPS
iptables -A INPUT -p tcp -i eth0 --dport 443 -m state --state NEW -j ACCEPT
# Allow icmp input so that people can ping us
iptables -A INPUT -p icmp -j ACCEPT
# Reject all other incoming packets
iptables -A INPUT -j REJECT