This is an old revision of the document!
See also ConfigServer Security & Firewall (CSF)
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/