This post shows how to to establish a synflood attack on an arbitrary remote host. 
The attack is performed using hping, which is free packet generator and analyzer for the TCP/IP protocol. 
Hping is one of the de facto tools for security auditing and testing of firewalls and networks. 
A syn-flood attack is basically a DOS-attack on a bug in TCP – some will argue that TCP is defective by design.
In most cases DoS attacks like this one renders a webserver totally unable to serve any requests from users.

The actual attack is initialized by this command:
hping -i u1 -S -p 80 dst-host-or-ip

Detailed info on attacking with Hping:
http://www.scribd.com/doc/607491/hping2-v1-5



To get hping installed on a Debian or Ubuntu-based system, type this to install:
aptitude install hping2
or download for *nix systems here: http://bit.ly/hpingLOIC



To install on a Windows system, download hping.exe and place it in your windows/system32/ and then open a command promp and type hping -h.
Download for Windows here: http://bit.ly/hping2LOIC