How to understand difference between telnet and ssh


Telnet and SSH are both network protocols that enable users to access and interact with remote systems. However, there are significant differences between the two, particularly in terms of security. In this article, we’ll explore the distinctions between Telnet and SSH, focusing on their protocols, security features, use cases, and practical considerations.

Telnet vs. SSH: Comparison Overview

Although Telnet and SSH have some similarities, there are many differences between the two. The most important is that SSH is much more secure than Telnet, which has caused it to replace Telnet almost completely in everyday use.

Telnet and SSH use different default ports. While Telnet can only transfer data as plain text, SSH can encrypt traffic in both directions.





Uses TCP port 23 and works best with local area networks.

Uses TCP port 22 by default. Easy to change the port number.


Less secure than SSH, with many vulnerabilities. Difficult to encrypt data.

Highly secure.


No authentication mechanism.

Uses public key encryption.

Data Formats

Data is transferred as plain text.

Data is transferred in an encrypted format via a secure channel.

Operating Systems

Linux and Windows.

All popular operating systems.

Bandwidth Usage



1. Protocols


Telnet utilizes a simple text-based communication protocol. It allows a user to establish a virtual terminal connection to a remote server, typically over TCP (Transmission Control Protocol) on port 23. Telnet sessions transmit data in plain text, making it susceptible to interception and unauthorized access.

SSH (Secure Shell):

SSH, on the other hand, employs a more secure protocol. It encrypts the communication between the client and the server, providing a secure channel over an insecure network. SSH commonly operates over TCP on port 22, and it supports various encryption algorithms, ensuring confidentiality and integrity of data during transmission.

2. Security


One of the critical drawbacks of Telnet is its lack of security features. All data, including usernames and passwords, is transmitted in plaintext, making it vulnerable to eavesdropping attacks. This inherent lack of encryption poses a significant security risk, especially when used over untrusted networks like the internet.


SSH, in contrast, was designed with security as a primary consideration. It encrypts the entire session, preventing unauthorized access to sensitive information. This encryption extends to passwords, commands, and any data exchanged during the session. SSH employs public-key cryptography, making it significantly more resistant to various types of attacks.

3. Authentication


Telnet relies on simple username and password authentication. As mentioned earlier, these credentials are transmitted in clear text, making them susceptible to interception. There is no built-in mechanism for secure authentication in Telnet.


SSH provides robust authentication mechanisms, including password-based authentication, public-key authentication, and multi-factor authentication. Public-key authentication is widely used for enhanced security, as it involves the use of cryptographic keys, making it more resistant to password-based attacks.

4. Use Cases


Telnet is primarily used for non-secure, text-based communication. It is suitable for scenarios where security is not a concern, such as internal network management or debugging. However, due to its lack of security features, its usage is discouraged over untrusted networks.


SSH is the preferred choice for secure remote access. It is widely employed for administrative tasks, file transfers, and tunneling secure connections. SSH is crucial for accessing and managing remote servers, especially when dealing with sensitive data.

5. Practical Considerations


While Telnet is still available on many systems for compatibility reasons, it is strongly recommended to avoid its use, especially over the internet. The clear text transmission of data makes it an insecure option for modern network communication.


SSH is the modern and secure alternative to Telnet. It has become the standard for secure remote access, offering a robust set of features for authentication, encryption, and secure communication. When connecting to remote systems or devices, SSH is the protocol of choice for ensuring data confidentiality and integrity.


In summary, the choice between Telnet and SSH boils down to security requirements. Telnet, with its lack of encryption, is suitable for non-sensitive and internal communications. SSH, with its robust security features, is the go-to option for secure remote access over untrusted networks. Understanding the differences between these two protocols is crucial for making informed decisions about the security of your network communications.

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