Port 23: Telnet
Port 23 is Telnet, an old remote-login protocol that sends everything, including passwords, in clear text. It has been replaced by SSH on port 22 and should be disabled where possible.
TCPRemote accessUnencrypted by defaultIANA assigned
| Port number | 23 |
|---|---|
| Service | Telnet remote login |
| Protocol | TCP |
| Category | Remote access |
| Default encryption | No |
Security note. Port 23 is not encrypted by default. Restrict it to trusted networks, or use an encrypted alternative where one exists, to avoid exposing credentials and data in transit.
Frequently asked questions
What is port 23 used for?
Port 23 is Telnet, an old remote-login protocol that sends everything, including passwords, in clear text. It has been replaced by SSH on port 22 and should be disabled where possible.
Is port 23 TCP or UDP?
Port 23 (Telnet) uses TCP.
Is port 23 secure?
Port 23 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 23 on my firewall?
Only if you specifically need Telnet. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.