sudo iptables -P INPUT DROP
sudo iptables -P OUTPUT DROP

# accept incoming connections on the SSH port of 22
sudo iptables -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
# accept incoming connections on the HTTP port of 80
sudo iptables -A INPUT -p tcp --dport 80 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
# accept incoming connection to LoopBack. Neccessary to provide full functionality to most services
sudo iptables -A INPUT -i lo -j ACCEPT

# accept outgoing connection to LoopBack. Neccessary to provide full functionality to most services
sudo iptables -A OUTPUT -o lo -j ACCEPT