Port 23: Telnet

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Port 23 is primarily used for Telnet, a network protocol that allows users to remotely access and manage devices over a network. However, Telnet is considered insecure because it transmits data, including login credentials, in plaintext, making it vulnerable to eavesdropping and man-in-the-middle attacks.

Key Points About Port 23:

  • Protocol: Telnet (Transmission Control Protocol – TCP)

  • Function: Remote command-line access to devices (e.g., routers, switches, servers)

  • Security Risk: No encryption, making it susceptible to attacks

  • Replacement: Secure Shell (SSH, port 22) is recommended instead of Telnet

Why is Port 23 Still Used?

Some legacy systems and embedded devices still rely on Telnet for remote management. However, most modern systems disable Telnet by default due to its security vulnerabilities. In real world we’re using using the telnet & attacker took the advantage of vulnerabilities associated with port 23.

Port 23: Telnet
Port 23: Telnet

How to Secure Systems Using Port 23:

  • Disable Telnet and use SSH (port 22) instead

  • Use firewall rules to block or restrict access to port 23

  • Implement VPNs or secure tunnels if Telnet must be used

  • Enable network monitoring to detect unauthorized Telnet connections

Security Risks Associated with Port 23:

  • No Encryption – Data, including credentials, is sent in plain text.

  • Brute-Force Attacks – Weak authentication makes it easy for hackers to guess passwords.

  • IoT Exploitation – Many devices ship with Telnet enabled, making them vulnerable to botnets.

  • Man-in-the-Middle (MitM) Attacks – Hackers can intercept and modify commands.

  • Remote Code Execution – Attackers can execute malicious commands on compromised devices.

  • Lack of Logging & Monitoring – Many Telnet implementations lack detailed security logs.

  • Firewall Evasion – If improperly configured, attackers can bypass firewall restrictions.

Best Practices for Securing Port 23:

  • Disable Telnet and Use SSH (Port 22)

  • Block Port 23 on Firewalls

  • Use Strong Authentication (Strong Passwords, MFA)

  • Restrict Access with IP Whitelisting

  • Monitor and Log Telnet Activity

  • Encrypt Telnet Sessions (VPN, TLS-Wrapped Telnet)

Common Commands for Port 23 (Telnet)

  • telnet [IP/Hostname] [Port]

  • telnet open [IP/Hostname] [Port]

  • telnet close

 

Get more technical details about Port 23 from SpeedGuide.

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