Port 137 — NetBIOS Name
Quick reference for TCP/UDP port 137, used by NetBIOS Name. Includes what the service does, security guidance and related ports.
What is port 137?
NetBIOS name service.
What port does NetBIOS Name use?
NetBIOS Name listens on port 137 by default.
Is port 137 open? How to check
Run one of these from your computer, replacing HOST with the IP address or domain you want to test.
nc -zvu HOST 137
Test-NetConnection HOST -Port 137
nmap -sU -p 137 HOST
A refused or timed-out connection means the port is closed or filtered by a firewall.
Security guidance
High risk — do not expose to the internet
Port 137 (NetBIOS Name) 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 137 used for?+
Port 137 is the standard TCP/UDP port for NetBIOS Name. NetBIOS name service.
What port does NetBIOS Name use?+
NetBIOS Name listens on port 137 by default.
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