Limit the number of incoming TCP connections
sudo iptables -N syn_flood
sudo iptables -A INPUT -p tcp --syn -j syn_flood
sudo iptables -A syn_flood -m limit --limit 1/s --limit-burst 3 -j RETURN
sudo iptables -A syn_flood -j DROP
sudo iptables -A INPUT -p icmp -m limit --limit 1/s --limit-burst 1 -j ACCEPT
sudo iptables -A INPUT -p icmp -m limit --limit 1/s --limit-burst 1 -j LOG --log-prefix PING-DROP:
sudo iptables -A INPUT -p icmp -j DROP
sudo iptables -A OUTPUT -p icmp -j ACCEPT