What we mean by NOPs generator and payload encoders

[natron at invisibledenizen.org (natron)]

The two following books have well written sections on exploitation of
buffer overflows, etc:

Gray Hat Hacking, 2nd Edition
http://www.amazon.com/Gray-Hacking-Second-Shon-Harris/dp/0071495681

Hacking: The Art of Exploitation, 2nd Edition
http://www.amazon.com/Hacking-Art-Exploitation-Jon-Erickson/dp/1593271441

-n

On Fri, Apr 10, 2009 at 9:20 AM, MaXe <metafan at intern0t.net> wrote:
> Deependra Singh Shekhawat wrote:
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> > Hello guys,
> >
> > Started with metasploit few weeks back. Still learning and reading about
> > it. While reading about the architecture of metasploit I came across NOP
> > generators.
> >
> > Now I have found that these are no operation generators (correct me if I
> > am wrong) used to let the exploit get un-detected from IDS.
> >
> > Can some one please elaborate more on NOPs and how they are generated as
> > well as how one can use them in creating one's own exploit or porting
> > any existing exploit to the metasploit framework ?
> >
> >
> > Also I have one doubt about Encoders , I read that encoders are used to
> > encode the payloads and probably they get decoded at the target machine,
> > can you please explain how this process happens and what basically
> > triggers this ?
> >
> > Thanks for the great stuff , guys . Really appreciate it as I read more
> > about it.
> >
> > ~jeevanullas
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> > _______________________________________________
> > https://mail.metasploit.com/mailman/listinfo/framework
>
> A good way to learn more about NOP Generators and also get more information
> about NOP sledges is to read about Buffer Overflows! :-)
> http://en.wikipedia.org/wiki/Buffer_overflow
> Of course there are many other good resources and i guess even one from here
> could explain how it works as well though shortly said it's used to make
> sure you will execute your payload :-) Stability for payloads is also
> another phrase that could fit. It's simply due to different kinds of systems
> may not execute an exploit 100% the same, so we add NOP sledges / slides :-D
>
> About encoding and decoding payloads which is a bit more tough, there are a
> few resources on Wikipedia which elaborates about Polymorphic Code:
> http://en.wikipedia.org/wiki/Polymorphic_code
> Of course there are other ways to encode a payload and my knowledge about
> this topic doesn't go that far, except that there is an encoded section and
> a section with a "decryption key". There is another "concept" which is
> called Mutating Code, that's something that is quite interesting as well ;-)
>
> I hope i answered your questions sufficiently. I might be a little wrong,
> but not totally though i must admit that Polymorphic Code doesn't have much
> to do with Metasploit, not sure..
>
>
> Best Regards,
> MaXe
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