Internet-Security.com UDP port 137 details

UDP port 137 is used by NetBIOS Name Service (NBNS), part of NetBIOS over TCP/IP, in Microsoft Windows for local network name registration and resolution used by SMB/CIFS file sharing.
Windows clients and servers (e.g., Windows 10/11; Windows Server 2016/2019/2022) communicate on UDP 137 for workgroup/domain name discovery.
Samba’s nmbd daemon on Linux/Unix uses UDP 137 to provide NBNS for SMB interoperability; many NAS devices (e.g., Synology, QNAP) and some printers expose it for Windows network discovery.
Microsoft WINS servers and clients use UDP 137 for centralized NetBIOS name registration and lookup.
Tools such as nbtstat (Microsoft) and nbtscan (third-party) query UDP 137 to enumerate NetBIOS names.
Security: UDP 137 is commonly abused for NBNS spoofing/poisoning (e.g., with Responder) to capture credentials on LANs and for reflection/amplification DDoS; exposing it publicly can leak host and workgroup names.

UDP 137