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Telnet vs. SSH

Instructor: David Delony

David is a freelance writer specializing in technology. He holds a BA in communication.

Both Telnet and SSH allow you to access a computer remotely. In this lesson, we'll learn about the differences between the two and their respective advantages, and also take a closer look at some of the features of SSH.

Telnet Vs. SSH

If you're looking to log in to a remote computer across a network, you have a choice between using SSH or the older Telnet protocol. What's the difference between the two and why would you want to use one more than the other. In this lesson, you'll learn the key differences between SSH and Telnet.

Telnet

Telnet is much older than SSH, predating SSH by about 25 years. Telnet was created when the network that evolved into the modern Internet, ARPANET, only connected a few universities and research labs in the U.S.

The goal of ARPANET was to allow researchers to share resources with the ultimate goal of improving the state of the art of computing and networking. It was very important to make it as easy as possible for other users to access things, so there was less emphasis on security in the late 1960s and early '70s than there is today.

There were simply no malicious users back then. Almost everybody on ARPANET was an experienced computer user and bringing down remote machines would have only hurt the project.

The lack of concern for security back then manifests itself in a lack of encryption. Everything sent over the network between the two computers is sent in cleartext, or completely unencrypted text. Anyone who intercepts the connection can read everything being sent. The major security problem is that this includes the usernames and passwords.

For example, a system administrator who logs in using the root account on a Linux system might be intercepted by a hacker. The hacker, realizing that someone logged in using the root account, will be able to use the password to log in.

The root account is allowed to modify any file on the system. With this power, an unauthorized user can do a lot of damage, such as deleting all the files or locking out other users.

For this reason, SSH is vastly preferred for remote connections. Telnet is best used for applications over trusted networks such as LANs that don't have a connection to the outside world and devices that don't support SSH at all. These are usually embedded devices. These devices should also be placed on networks that are isolated from the Internet for security.

SSH

SSH or Secure Shell offers a much more secure connection to a remote computer.

The biggest advantage of SSH is that the connection between the host and the remote computer is encrypted. This means that an outside user who manages to intercept the connection will only see an apparently random string of numbers and letters instead of cleartext.

This makes SSH much more useful for remote logins where security is needed.

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