sorry for the boring answer, but welcome to the wonderful world of TCP/IP
A SYN flood is an exploit of the TCP/IP protocol (redundant, i know.) which you use when you are online.
A TCP connection makes a 3-way handshake. The connecting host sends a SYN packet to the receiving host. The receiving host sends a SYN/ACK packet back. The connecting host responds with an ACK to establish the connection.
In a SYN flood, the connecting host sends several SYN requests to the receiver, but when the receiver sends back the SYN/ACK packet, the connecting host doesn't respond with a final ACK.
Essentially, you open up a bunch of connections on a machine, filling up its buffer until it can no longer properly process requests.
I believe ISS has software that minimizes this problem. It's called 'RealSecure' or something like that.
There are lots of scripts out there for doing such a thing, so I'm not going to tell you how to do it. I believe Phrack magazine made it popular knowledge.
Obligitory knife banter: What knife would you use to skin a person who SYN floods your favorite web site and brings it down? Would you use a variety of knives for different tasks, or would you just lop off limbs with a Battle Mistress or a Kukhri?
Or are firearms more suitable for such as task
[This message has been edited by TomMarker (edited 16 June 1999).]