what is exactly a buffer overflow ( sending packets ) how to do it ?

Posted a tutorial I had in my favorites for a while, very good for beginners:
http://forums.governmentsecurity.org/index...=ST&f=15&t=1995

Also, recommend reading "Smashing The Stack For Fun And Profit" by Aleph one
(http://www.maths.leeds.ac.uk/~read/bofs.html)

Hope this helps mate!

thank u for all , does it exist a programm to do it automaticly from an ip ?

Remote exploits/DoS (buffer overflow kind) work like a normal exploit but instead they then send the shellcode (exploit) or large junk string (DoS) over a socket so in order to create a remote exploit/DoS you must know socket programming.

Guide to *nix socket programming.
http://www.ecst.csuchico.edu/~beej/guide/net/html/

Hoped this has helped, if I didn't answer your question please refrase your question as I was a little confused on what you were exactly asking.

thank u all for your great helping i hope to learn quick ( i am usually lazy but i behave )

I would like to ask that, How an what is the meaning of 'Crafting 3k Buffer overflow'? After finding IIs vuln.
Hope that somebody solve my problem....Great Appreciation...TQ.