Both Telnet and Secure Shell (i.e. SSH) are network protocols used to connect to remote servers and both have been used widely at different points in time. Telnet is the original protocol that was used when the internet was first launched in 1969. It was developed to be used in private networks and has no security measures, making it irrelevent when used on public networks. This is the main reason why SSH was developed as a replacement for Telnet. We will discuss the differences between telnet and SSH, however lets first understand what each one is.
What is TELNET?
Telnet is a remote protocol that allows a user to communicate with a remote device. It is an abbreviation for: Terminal Network, Telecommunication Network or Teletype network, depending on the source. It was originally built to be a form of remote control to manage mainframe computers from distant terminals. Telnet is a text-based computer protocol, meaning it does not contain a GUI (i.e. Graphical User Interface). The three types of basic services that Telnet offers are:
- Determining a virtual network terminal that renders a standard interface to remote systems.
- Providing a set of standard options and includes a mechanism that permits the client and server to transact options.
- Allowing an arbitrary program to become a client or either end can negotiate options.
Due to the lack of security measures, Telnet has been almost completely replaced by SSH in nearly all usage scenarios.
What is SSH?
Secure Shell is a network protocol that gives users a secure way to access a computer over an unsecured network. It provides several alternative options for strong authentication, and it protects the communications security and integrity with strong encryption. Unlike Telnet, once an SSH connection is established, the data that is transmitted is encrypted according to the parameters negotiated in the setup in accordance to industry standard strong encryption algorithms (e.g. Advanced Encryption Standard). During this stage, the client and the server both agree on the symmetric encryption algorithm to be used and generate the encryption key. The typical uses of the SSH protocol:
- Providing secure access for users and automated processes
- Interactive and automated file transfers
- Issuing remote commands
- Managing network infrastructure and other mission-critical system components.
Key Differences Between Telnet and SSH
Even though both protocols server the same purpose, Telnet is a conventional protocol whereas SSH is the replacement for Telnet, also providing some enhanced features.
Telnet transmits all data in plain text format (yes, even passwords), allowing for anyone on the network to be able to intercept the traffic and effortlessly access it. As one can imagine, this is a tremendous security risk and is the primary reason why Telnet is nearly extinct today.
SSH on the other hand, uses encryption for all transmitted layers, making security breaches less likely to occur and allowing it to withstand eavesdropping, man-in-the-middle and insertion/replay attacks.