:syn-flood - [0:0]
...
-A INPUT -p icmp -m limit --limit 1/sec --limit-burst 10 -j ACCEPT
-A INPUT -f -m limit --limit 100/sec --limit-burst 100 -j ACCEPT
-A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,ACK SYN -j syn-flood
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A syn-flood -p tcp -m limit --limit 3/sec --limit-burst 6 -j RETURN
-A syn-flood -j REJECT --reject-with icmp-port-unreachable
