Packets (R&W)

Packets:

I know some about them, but:

A) How can I catch one and read it (sniffer perhaps?)

B) Is there any way I can write one?

and

C) Is there any way to mess with the protocols that send them and/or which ports are used?
:confused:

Sniffer will capture packets also another good proggie for that is Ethereal (both windows and *NIX).

Before I answer your other question I have one for you. What legitimate purpose would you have to fool around with a packet if you're going to send it out? You have a limited understanding of TCP/IP what would you gain by it?

From the tutorials index

1: Packet Sniffing(tcpdump install and first use) by IchNiSan
2: Packet sniffing. written by yours truly.

That is some reading material regarding your first question.
For the second question:
Yes it is possible to handcraft packets. Get some information on how TCP/IP works. From the formatting of your questions I doubt your reasons on why you want to do this a bit.
If you want to learn how the different protocols laying on top of TCP/IP work I suggest you go read some rfc's (request for comments).
You can find a complete list of rfc's @:
http://rfc-editor.org/
To find out about the diferent ports being used you can either search this forum or use a search engine like google.

Buenos Dias
noODle ::bandit::

Quote:

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Is there any way to mess with the protocols that send them and/or which ports are used?

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The protocols are well documented in RFCs http://directory.google.com/Top/Comp...net/Protocols/

A protocol can be thought of as a language for comuncation, from one application to another usualy over a network such a the Internet. The end points of the comunication each understand the language. You can make your own protocols to use between your own applications.

Quote:

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What legitimate purpose would you have to fool around with a packet if you're going to send it out? You have a limited understanding of TCP/IP what would you gain by it? [/B]

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I'll be honest, I have absolutely no proof that I wouldn't use this info for hacking.
All I have to offer is my word that I just want to know, and the fact that I probably woudn't have the brass ones needed for an evil hack.

Hey, if I know about it, who says I can't re-write it and add yet another layer of security to my pc? (This is being hypothetical)

I don't have a legitimate purpose, but, then again, I don't have any purpose. ;)

Here are two packet writers that I use on a regular basis:

For Windoze: Packet Crafter It will be useless to you if you don't understand TCP/IP. It has no documentation so either you understand or you don't.

For LOONIX: Hping Again, if you don't understand protocols and packets then this will be useless to you.

I'm giving you these links for two reasons. One, I don't think you have the technical capability to harm anyone at this point. Two, I'm assuming that you will use these tools to legitimately learn about packet content and structure to hopefully become security-aware.

--TH13

MR.CD:\ is nice boy
MR.CD:\ not harm anyone
MR.CD:\ actually afraid fuzz lock him up with "lonely" men in big house if he do
MR.CD:\ just want to learn

{This philosophy to be applied to all my posts}