Feel free to use the following iptable commands below to drop INVALID SYN packets that sometimes are also used to flood the server..
/sbin/iptables -A INPUT -i eth0 -p tcp --tcp-flags ALL ACK,RST,SYN,FIN -j DROP
/sbin/iptables -A INPUT -i eth0 -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP
/sbin/iptables -A INPUT -i eth0 -p tcp --tcp-flags SYN,RST SYN,RST -j DROP
--
Jeff @ LinuxAdmin