Port 23

Q: What is port 23?

Obsolete unencrypted remote terminal protocol Telnet was the first widely used remote access protocol, but it transmits everything — passwords, commands, and data — as unencrypted plaintext, making it trivially vulnerable to network sniffing. It has been fully superseded by SSH (port 22). Today it is used only for low-level network debugging (e.g., testing TCP connectivity to a specific port). An open port 23 on a public-facing server is a serious security red flag that should be addressed immediately.

Telnet

Obsolete unencrypted remote terminal protocol

Port

Protocol

TCP

Service

Telnet

Security

Dangerous

Full name: Telnet

What is port 23?

Telnet was the first widely used remote access protocol, but it transmits everything — passwords, commands, and data — as unencrypted plaintext, making it trivially vulnerable to network sniffing. It has been fully superseded by SSH (port 22). Today it is used only for low-level network debugging (e.g., testing TCP connectivity to a specific port). An open port 23 on a public-facing server is a serious security red flag that should be addressed immediately.

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