SSH vs TELNET: Key Differences and When to Use Each

SSH (Secure Shell) is a secure protocol that encrypts data for remote access, while TELNET sends data in plain text without encryption. SSH is preferred for secure communication, whereas TELNET is mostly outdated and used only in trusted or legacy environments.

Quick Comparison

This table summarizes the main differences between SSH and TELNET.

Feature	SSH	TELNET
Security	Encrypts all data including passwords	Sends data in plain text, no encryption
Port Number	Default port 22	Default port 23
Authentication	Supports strong authentication methods	Basic username and password
Use Case	Secure remote login and command execution	Legacy remote login, less secure
Data Integrity	Ensures data is not tampered	No data integrity checks
Popularity	Widely used today	Rarely used, mostly legacy systems

Key Differences

SSH is designed to provide a secure channel over an unsecured network by encrypting all transmitted data. This protects sensitive information like passwords and commands from being intercepted by attackers. It also supports various authentication methods such as public key authentication, making it more secure and flexible.

In contrast, TELNET transmits data in plain text, which means anyone monitoring the network can easily read the information, including login credentials. Because of this lack of security, TELNET is considered unsafe for use over the internet or untrusted networks.

Additionally, SSH includes features like data integrity checks and compression, which TELNET lacks. SSH uses port 22 by default, while TELNET uses port 23. Due to these security and feature differences, SSH has largely replaced TELNET in modern network environments.

SSH Code Comparison

python

import paramiko

# Create SSH client
client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())

# Connect to remote server
client.connect('example.com', username='user', password='pass')

# Execute command
stdin, stdout, stderr = client.exec_command('ls -l')

# Print output
print(stdout.read().decode())

# Close connection
client.close()

Output

total 0
-rw-r--r-- 1 user user 0 Apr 27 12:00 file1.txt
-rw-r--r-- 1 user user 0 Apr 27 12:00 file2.txt

TELNET Equivalent

python

import telnetlib

host = 'example.com'
user = 'user'
password = 'pass'

# Connect to remote server
tn = telnetlib.Telnet(host)

# Login
tn.read_until(b"login: ")
tn.write(user.encode('ascii') + b"\n")

tn.read_until(b"Password: ")
tn.write(password.encode('ascii') + b"\n")

# Execute command
tn.write(b"ls -l\n")

# Read output
output = tn.read_until(b"$").decode('ascii')
print(output)

# Close connection
tn.write(b"exit\n")
tn.close()

Output

file1.txt
file2.txt
$

When to Use Which

Choose SSH when security is important, such as accessing servers over the internet or untrusted networks. SSH protects your data and credentials with encryption and strong authentication.

Choose TELNET only in trusted, isolated networks or legacy systems where encryption is not required or supported. TELNET might be used for simple testing or on devices that do not support SSH, but it should be avoided for sensitive tasks.

Key Takeaways

SSH encrypts data and is secure; TELNET sends data in plain text and is insecure.

SSH uses port 22 and supports strong authentication; TELNET uses port 23 with basic login.

SSH is the modern standard for remote access; TELNET is mostly obsolete and risky.

Use SSH for any remote connection over untrusted networks.

TELNET should only be used in safe, controlled environments or legacy cases.