Telnet

Telnet is a user command and an underlying TCP/Ip protocol for accessing remote computers. With the Telnet command, you as an administrator or another user can access someone else’s computer remotely.

On the Web, HTTP and FTP protocols allow you to request specific files from remote computers, but not to actually be logged on as a user of that computer. With Telnet, you log on as a regular user with whatever privileges you may have been granted to a given application or data on that computer.

The result of the telnet requesting command would be an invitation to log on with a User ID and a prompt for a password. In case it is accepted, you would be logged on like any user who used this computer every day. Telnet generally comes after SSH for remote system management from the command line.

Brief history of Telnet

This protocol was created with the computer networks, it was designed as a simple TCP/IP protocol. After a research protocol which was developed by DARPA named computer network created. Computer network made the computers available from remote for management and usage. Telnet was created as a remote command-line interface management protocol. The first usage of the telnet protocol was in 1969.

Telnet architecture is composed of the client and server model that is, Server side provides telnet service to connect from a client telnet applications. Telnet server side generally listens for TCP 23 port to accept telnet connections. However, you must note that this port can be changed for security or other reasons.

Features of Telnet

Telnet protocol provides following features for remote system management.

• Simplicity
• Display connection information
• Fast
• Secureless

Devices that support Telnet

Here is a list of devices that uses telnet for remote management.

• Linux
• Router
• Switch
• Firewall
• Router
• Camera
• IoT
• Windows
• Raspberry Pie
• Cisco IOS

How to Install Telnet in Windows 10

I will take you through two methods that you can use to install Telnet on your windows machine, that is the using the control panel and also using the command line option.

Using the control panel

• Open “Control Panel“.
• Open “Programs“.
• Select the “Turn Windows features on or off” option.
• Check the “Telnet Client” box.
• Click “OK“. A box will appear that says “Windows features” and “Searching for required files“.When complete, the Telnet client should be installed in Windows.

Using the Command Line

• Hold down the Windows Key, then press “R“.
• The Run dialog box appears.
• Type: pkgmgr /iu:”TelnetClient”
• Select “OK” and Windows will install the Telnet client.

Telnet Security is weak

Telnet protocol is not encrypted which makes it vulnerable to the man in the middle-security attacks. This is the biggest problem with Telnet. The telnet traffic can be readable if someone can sniff the traffic from the network. Encryption makes it unreadable by others other than the remote part. Telnet also provides only password-based authentication and since passwords are transmitted over the network, they can be caught by attackers.

Encrypt Telnet with Telnet/s

Telnet protocol does not encrypt its traffic. If we want to encrypt traffic we can use Telnet/s which encrypts the traffic. Actually, some TLS/SSL tunnel is created and telnet traffic is transmitted through this TLS/SSL tunnel. In fact TLS/SSL implementation is the reason Telnet/s is not used widely.

Telnet commands commonly used

Command	Command name
$ telnet	Start Telnet Interactive Shell
> h > help	Help Command
> o 192.168.142.138	Open Command
> close	Close Command
> display	Display Command
> quit	Quit Command
> set ?	Set Command
> status	Status Command
> unset ntlm	Unset Command

pen Ports

Using telnet [domainname or ip] [port] will allow you to test connectivity to a remote host on the given port. That is, telnet [domain name or ip] [port]

Put the IP address or domain name of the server you’re trying to connect to in place of [domain name or ip], and replace the second brackets with the port number on the remote machine, connection to which you want to test.

Telnet Alternatives

• SSH provides better security by encrypting traffic and providing better and secure authentication. SSH also have a lot of extra features like X desktop forwarding, port forwarding etc. SSH is the biggest and better alternative to the Telnet protocol.
• RDP is not a command line remote protocol it is used as GUI based. RDP needs more network bandwidth but provides complete desktop experience.
• VNC is an opensource alternative which similar to the RDP protocol. It provides desktop remotely but slower than RDP in most cases.
• SNMP is designed for remote management over non interactive commands. But it is mainly used to monitor remote systems and not complete alternative to the telnet protocol.