Studying Telnet ... ..:: Sbenk - Official Website:: ..

Studying Telnet ...

Good title not

For now I'm starting to learn telnet who wants to deepen contacts with me and discuss it in private ..

I do not know why but I was always fascinated telnet: D..

Telnet is a network protocol used on the Internet. The IETF document STD 8 (RFC 854 and RFC 855) say:

The goal of the TELNET Protocol is to provide a sufficiently widespread support for communications, and bi-oriented byte (eight bits ).

It is usually used to provide remote user login sessions from the command line type of Internet hosts.

By extension, telnet is also the name of a program that a user can use to start a Telnet session to a remote host, the telnet program implements the client side of the protocol. Telnet clients are available on most Unix systems for many years and are available for any type of computer.

English to telnet is used as a verb and means to establish a Telnet connection.

Details of the protocol

Telnet is a client-server protocol based on TCP, and clients typically connect to port 23 on the server (although the door can be different, as for several Internet protocols). In part because of protocol design and partly due to the flexibility provided by the programs typically Telnet, you can use a Telnet program to connect to some other interactive service on an internet server. A classic use is to connect with telnet to port 25 (which typically is located on an SMTP server) to debug a mail server.

The Telnet protocol can be divided into a main part and a set of extensions. dell'IETF, che sono anche unite nell'STD 8, e definiscono le caratteristiche base del protocollo ed il modo di implementare le estensioni. The main part is described by IETF RFC 854 and RFC 855, which are also joined nell'STD 8, and define the basic features of the protocol and how to implement the extensions. Among the many extensions, some are adopted as Internet Standards. The STD documents 27 to 32 define various Telnet extensions, most of which are very common. Among the remaining extensions, the most important are those proposed by the IETF as a standard, further details can be found in STD 1.

As explained below, Telnet is not safe and should be generally avoided. Its use over public networks has serious security risks.

Security

There are three main problems related to Telnet, making it a bad choice for modern systems from the point of view of security:

In the Telnet daemon commonly used have been found over the years, many vulnerabilities, and probably others still exist.
Telnet does not encrypt data sent over the connection (even passwords) and is therefore trivial to capture the data exchanged and the password used for malicious purposes.
A Telnet lacks an authentication scheme that makes sure the communication between two hosts and not trappable.

In environments where security is important, as the public Internet, Telnet should not be used. The telnet sessions are not encrypted. This means that anyone with access to a router, switch or gateway located on the network between two hosts that are communicating via Telnet, can intercept the packets passing through it and easily get whatever is being traded (including user names and password) programs such as tcpdump and Ethereal.

These flaws have meant that the use of the Telnet protocol to fall rapidly in favor of the more secure SSH protocol, released in 1998. SSH provides all the functions of Telnet as a secure encryption, which prevents the interception of data exchanged, and public key authentication, which ensures the identity of the remote server.

, consigliano di interrompere l'uso di Telnet per login remoti in circostanze normali. The computer security experts, such as' SANS Institute and members of the newsgroup comp.os.linux.security, recommended to discontinue use of Telnet for remote login under normal circumstances.

When Telnet was developed in the early 80's, according to some sources even in 1969, most users of the networks belonged to the departments of academic institutions or research centers, private or government. In this environment, security was not as important as it is today, with the expansion of broadband. With the exponential growth in the number of people accessing internet, and the number of those who want to enter into others' systems, Telnet should not be used in Internet networks.

Use

Telnet clients are still used occasionally to "talk" to other services. Telnet is used occasionally in debugging network services such as SMTP and HTTP, as it represents an easy way to send commands to the server and examine the answers. Telnet can also be used as a rudimentary IRC client if you have an adequate knowledge.

Telnet is widely used for Multi User Dungeon games played over the network.

In the field of e-mail Telnet has many valid uses, for example, you can read letters on your mailbox, delete or send electronic letters ^[1]. Since you normally access to your mail box is done in an unsafe manner, or sometimes from a public computer, Telnet security problems are not an obstacle.

Sometimes you have problems with webmail access to their mailbox that can be solved with Telnet, for example in case of exceeding the memory block is given a few boxes and Telnet allows to solve the problem.

Another interesting feature of Telnet and e-mail is the ability to send anonymous email or fake email (fake emails). If no proxy is used by the judiciary, the police post is able to identify the sender via its IP address.

Telnet can be used by a common web browser, in the presence of a connection (usually HTTP) already active to an Internet Service Provider: Telnet is a protocol level higher than the level of data transport, and requires that a session is already begun.