Port 23 — Telnet
Quick reference for TCP/UDP port 23, used by Telnet. Includes what the service does, security guidance and related ports.
What is port 23?
Plain-text remote login. Insecure — disable on production routers.
What port does Telnet use?
Telnet listens on port 23 by default.
Security guidance
High risk — do not expose to the internet
Port 23 (Telnet) is high-risk because the service it carries is a frequent target for credential attacks, brute force or unpatched-vulnerability scanning. Keep it bound to localhost or your VPN, never forward it directly on a router, and require strong authentication.
Related ports
Frequently asked
What is port 23 used for?+
Port 23 is the standard TCP/UDP port for Telnet. Plain-text remote login. Insecure — disable on production routers.
What port does Telnet use?+
Telnet listens on port 23 by default.
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