Port 23 — Telnet

TCP · Port 23/TCP is used for Telnet, a protocol allowing remote access to a device's command-line interface. This service is often used for debugging and testing purposes, but its use can also be exploited by attackers to gain unauthorized access to systems.

Port Number: 23
Service Name: Telnet
Protocol: TCP
Common Software: telnetd, BusyBox telnet

Security Notes

Telnet is completely insecure. All data including credentials is sent in cleartext. Disable it and use SSH.

FAQ

What is port 23 used for?

Port 23 is used for Telnet. Port 23/TCP is used for Telnet, a protocol allowing remote access to a device's command-line interface. This service is often used for debugging and testing purposes, but its use can also be exploited by attackers to gain unauthorized access to systems. Common software: telnetd, BusyBox telnet.

Is port 23 dangerous to leave open?

Telnet is completely insecure. All data including credentials is sent in cleartext. Disable it and use SSH.

How do I check if port 23 is open?

Use nmap: nmap -p 23 <target> or check locally: ss -tlnp | rg 23