Telnet

From DrugPedia: A Wikipedia for Drug discovery

TELNET

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 r login program. Telnet allows you to control a remote computer from your own one. It is terminal emulation software. In the old days hard drives were humongous and expensive and there were no personal computers. To make use of existing computers you had to lease hard drive 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.

With telnet you can do various things like send mail, log in to irc or proxy and even 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 pressure your precious resources. Usually help or remote help 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, 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 favorite programs 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 similar 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 emails. The port to login to is 25. First you have to identify your self. This goes 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:[email protected] The server will give you feedback again telling you

/* ...Sender OK You are accepted. Now for the Receptient

/* RCPT TO:[email protected] again feedback

/* ...Receptient OK The server still 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

/* QUIT (or END, EXIT, LOGOFF LOGOUT) 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.

/* USER you@THE_SERVER_GOES_HERE.net /* 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 completely understanding telnet and how it works. They are a basic understanding of TCP/IP and a basic understanding of UNIX commands.

Where to use

You could use telnet to connect to a proxy and from there on continue your quest. Find a good proxy (use a search engine to locate one) and create an account. Now telnet to the server on the port specified on the website and hang loose. Using a proxy to use the web keeps your identity better hidden. Proxies often use port 8080 or 3128. If you use IE or Netscape you configure them to use a proxy. If you have computer friends maybe they could help you locate one nearby. To learn more about proxies read a tutorial about them. Telnet is part of TCP/IP and with this comes specific built in connection security. This basically 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.

There are several interesting ports for trying telnet like 7:echo. This one replies whatever you type in. 13 daytime 15 netstat 37 time 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. If you want to exploit a system use the info and go to exploiters.net. If you come across a system you don't know read the ALT.2600.FAQ.

If you have a root account on a telnet server you can use this to remotely administer the server. There are many ways 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 up to 9600 bps you might not want to load up the web.

U can use telnet to create a shell account. This allows you to use a good shell even though u use Microsoft OS. Shell accounts vary in the services they have available. To find a good shell account search the net or try freeshell.org. Look for a shell that offers the programs you did like to use.