This is an old revision of the document!
See also ConfigServer Security & Firewall (CSF)
http://www.opensourceforu.com/2011/04/securing-apache-part-8-dos-ddos-attacks/
Good Info on SYN Flood Issue: http://security.stackexchange.com/questions/15368/syn-flooding-issue
http://365hostingsupport.com/blog/dos-how-to-check-it/
http://linuxstuffs.wordpress.com/2009/10/25/drop-syncddos-attack/
netstat -alpn | grep :80 | awk '{print $4}' |awk -F: '{print $(NF-1)}' |sort | uniq -c | sort -n