Port 137 (NetBIOS Name Service) – TCP/UDP

TCP Yes

UDP Yes

SCTP —

DCCP —

What it is

NetBIOS name registration and resolution.

Legacy Windows networking. Block at the perimeter; LLMNR/NBT-NS spoofing is a common LAN attack.

Transport	Status	Meaning
TCP	Yes	Assigned by IANA and standardized, specified, or widely used on this port.
UDP	Yes	Assigned by IANA and standardized, specified, or widely used on this port.
SCTP	—	Not applicable for this transport.
DCCP	—	Not applicable for this transport.

« 135 MS RPC Endpoint Mapper 138 NetBIOS Datagram »

Well-known (0–1023). System port for a core service. On Unix-like systems, binding it requires superuser privileges.

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