Port 138 — NetBIOS Datagram
Quick reference for TCP/UDP port 138, used by NetBIOS Datagram. Includes what the service does, security guidance and related ports.
What is port 138?
NetBIOS datagram service.
What port does NetBIOS Datagram use?
NetBIOS Datagram listens on port 138 by default.
Security guidance
High risk — do not expose to the internet
Port 138 (NetBIOS Datagram) 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 138 used for?+
Port 138 is the standard TCP/UDP port for NetBIOS Datagram. NetBIOS datagram service.
What port does NetBIOS Datagram use?+
NetBIOS Datagram listens on port 138 by default.
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