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Thread: telnet

  1. #1


    This paper can be found at http://www.linuxadvisory.com/
    I wrote it. I decided to share it with the AO community.

    First of all what is telnet?

    Telnet is a protocol which is part of the TCP/IP suite. It is quite similar to the UNIX rlogin program. Telnet allows you to control a remote computer from your own one. It is terminal emulation software. In the old days harddrives were humonguous and expensive (i am talking waY back here) and there were no personal computers. To make use of existing computers you had to lease hardrive space and use terminals to operate the system. For developers this was great because computing became lots cheaper. You needed a server and many connections could be made. With telnet u can emulate this type of distributed computing and for example operate a supercomputer from a distance.
    TCP/IP works with ports and telnet has one also. It's nr 23. It's has several rfc's. Nr 854 dates back to 1983 and is named telnet protocol specification.
    With telnet you can do various things like send mail, log in to irc or proxy and even (though hardly anymore) view and modify websites. There are telnet services available allowing you to search through large databases using telnet. With this you use the remote computer's power so it won't presure your precious resources. Usually help or remotehelp are the commands to use to find out what you can and cannot do. If you can't see what you type in then set echo. Once you made a connection you can use the computer as if it was your own. You use command lines for this.
    Telnet knows different emulation types. VT-100 is most used. This emulation was used on the video terminals of DEC. There are still VT-100 servers running out there. Scientists use these.

    To use telnet you need a client. Windows has telnet built in by default (as does UNIX but that's a different story), but there are third party clients available on the net. You start a telnet session by typing in the command 'telnet server.net 23' where the port number is optional. Since Telnet was based on UNIX (as it is part of TCP/IP which also was based on UNIX) it uses UNIX commands. Basic knowledge would help you here. The port number specifies what services you will use. 23 is the default one. You can log into various services. 80 is the HTTP server for that.
    So say you wanted to modify your site from a distance on a leased line. You don't have your fav progs and hardly any time.
    /* telnet server.net 80 (leave the /*)
    /* GET http://www.server.net/YOURSITE.HTM HTTP/1.1
    You can use this method to get the output of a cgi-script as well. The simple request doesn't use the HTTP/1.1 (this is the HTTP version running on the server). If you perform a bad request you usually get some info on the server. Use this to find a the correct versions of services running.
    To put files to the server u use the PUT command. Telnet is pretty simillar to FTP which is also part of TCP/IP. There are other commands available like POST, which is used to put larger data files to the server, HEAD to get the sites header and DELETE. This one is obvious isn't it.
    You can also use telnet to send raw imails. The port to login to is 25.
    First you have to identify your self. This geos like this:
    /* telnet mail.server.net 25
    /* HELO www.you.net
    When you typed this command you'll get some feedback telling you who and what you logged on to. When you login u may get also some feedback telling you things. :`;
    After this you tell the server where the mail is from like this:
    /* MAIL FROM:you@youradress.net
    The server will give you feedback again telling you
    /* ...Sender OK
    You are accepted. Now for the receipant
    /* RCPT TO:yourroommate@hisadress.net
    again feedback
    /* ...Receptient OK
    The server stil does it's duty.....
    /* DATA
    After typing this command you'll get the instructions on the proper way to send the mail. Type your mail using the instructions. After you're done sending your mail close the connection using
    You can use this to receive your mail as well (if your provider allows you). The POP port is 110. Telnet to the server on this port. Once there use the following commands.
    /* PASS ;type in your password (simple huh.).
    Once you are accepted as a valid user use the following to list your mail.
    /* LIST
    Ports can be configured so they may be different on some systems. Many admins use the default ones though.

    Two things come in handy when completly understanding telnet and how it works. They are a basic understanding of TCP/IP and a basic understanding of UNIX commands.

    Telnet is part of TCP/IP and with this comes specific built in connection security. This basicly comes down to the three-way-handshake which i will not furtherly discuss in this tut. Terminal emulation was embraced by developers because it is a quick and secure way for remote computing.

    Bcause telnet is developed to be quick and reliable you could use it to connect yourself to an irc-server and chat with your buddies without a resource consuming GUI. You may even want to use a proxy to keep the (f)lamers from finding out your ip. To do this you have to know that the irc protocol has it's ports dedicated to 6666:6669. Ports can be configured so you have to know to what port you should connect. The identd runs on port 113. Better use a shell account to connect to IRC servers or a GUI client. Once you are there u can use the usual irc commands. If you have got a good shell (command.com) you can use scripts to automate procedures. To learn more about irc: Request for Comments: 1459 Internet Relay Chat Protocol. mIrc is a pretty good irc-client for nowadays high resource conputers if you want to learn this to. Since linux was built on UNIX and linux is free, you should have by now installed this operating system. OK
    U can also post to newsgroups if the server allows this. Newsgroups use nntp (rfc 977) over port 119. Use your skills. If you want to get information on a particular system you can use a technique known as port scanning. There are pretty fancy port scanners on the net but to become a guru you will have to know how hits take place. So use port surfing instead. Telnet to the server on various ports to get info on services. This is much more rewarding then using someone else's portscanner. If you want to become a good hacker learn a programming language and write your own. Because TCP/IP is not designed for a specific platform it works much the same on any. TCP/IP uses ports that have certain services.
    There are severel interresting ports for trying telnet like 7:echo. This one replies whatever you type in.
    13 daytime
    15 netstat
    37 time
    39 rlp
    53 domain
    119 nntp
    443 https

    Use your commands to get the requested info. By connecting to different services you get a clear look at the system in use.
    The expansion of free software towards the windows market gives great tools to set up your own hackerlab. For this you use your computer and one other. Set up a simple network with a server.
    Configure the server and start hacking.
    If you have a root account on a telnet server you can use this to remotely administer the server. There are many wats to get a root account. Remember that if an administrator finds a new root account on his system he will know it has been tampered with. Covering your tracks is fatal if you want to stay uncaught. Telnetting from a PDA is a pretty fancy way to read your mail or post to newsgroups from a distance. Because GSM phones can only transmit upto 9600 bps you might not want to load up the web.

    To have a more secure terminal connection you could use secure shell.

    Hope you enjoyed it.


  2. #2
    I have recieved some reply that I plagerized it.
    This tut can be found on hackergurus.com

    If you are are in doubt.
    Send a mail to the address listed on the site then i will let you know that I did write that !

  3. #3
    AntiOnline Senior Member souleman's Avatar
    Join Date
    Oct 2001
    Flint, MI
    you bitch about tonybradly then you come in here and copy/paste an entire tutorial from a different site and don't even take the time to cite your source or say that it is a copy paste or link to it? And you did it what, 30 to 45 minutes AFTER we had the discussion about copywrite in IRC where I was talking about being able to get sued for doing this?

    Do you not remember this conversation????
    [11:41] <+Blaze> he could have posted it all in one thread
    [11:41] <souleman> which he is only doing because of copywrite laws
    [11:41] <souleman> no he couldn't Blaze
    [11:41] <souleman> it would be illegal
    [11:41] <+Blaze> how come ?
    [11:41] <souleman> just because most of the idiots on the site don't understand the word copywrite
    [11:42] <souleman> because he doesn't OWN the tuts
    [11:42] <souleman> he wrote them but then they were sold to about.com
    [11:42] <souleman> so he doesn't have ownership any more
    [11:42] <souleman> so if he posted them in 1 thread, it would be a copywrite violation and both him and antionline could be sued for it
    [11:43] <+Blaze> ah ok sorry then
    [11:43] <souleman> and because he is actually intelligent enough to realize that, people bitch about it
    \"Ignorance is bliss....
    but only for your enemy\"
    -- souleman

  4. #4
    Junglist Switch

    To: dos_cerveza@mail.com
    Subject: plagerism?
    Date: Fri, 18 Apr 2003 16:49:11 +0000


    Some one is using the material from - >

    The person is question ->

    He/She Claims to be you?

    Now I am sorry I am bitching bout tb's post before.
    Like I said the same IRC session.

    I was a bit to quick in my reply.

  5. #5
    AntiOnline Senior Member souleman's Avatar
    Join Date
    Oct 2001
    Flint, MI
    if it is your tut (which it appears to be since you got that mail from whoever sent it to you) then say it ahead of time. Come right out and say, I wrote this tut and put it on linuxadvisary.com or whatever at the start of the tut. So that no one jumps to conclusions. I am going to give someone the benifit of the doubt unless they are known for copy/pasting other peoples tuts, as long as they say what is up from the beginning. Sorry for the accusation, but even you gotta admit that it looks pretty bad when you didn't say anything and you used different nick's on different servers.
    \"Ignorance is bliss....
    but only for your enemy\"
    -- souleman

  6. #6
    Trumpet-Eared Gentoo Freak
    Join Date
    Jan 2003
    Well noodle,

    You wrote it, period.
    I like it and I would like to see more from where that came from.

    Good job.
    Come and check out our wargame-site @ http://www.rootcontest.org
    We chat @ irc.smdc-network.org #lobby

  7. #7
    Junior Member
    Join Date
    May 2002
    whoever wrote it, thanks alot. it helps.
    [shadow]LIFE IS GOOD[/shadow]

  8. #8

  9. #9
    Join Date
    Dec 2002
    No0Dle, can i post ur tut next...

    i think we should all have a go?!?!



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