UDP Port 137 – NetBIOS Name Service (NetBIOS-NS)

About UDP Port 137

Port 137 carries the IANA assignment for netbios-ns. The IANA description reads: ‘NETBIOS Name Service’. This port appears in 6 IDS rules and does not have notable malware activity indicators in our data.

IDS Rule References

6 IDS / security rules reference UDP port 137. Presence in IDS rules does not mean traffic on this port is malicious. These are patterns security tools monitor.

Rule categories (top 2): attempted-admin (5), attempted-recon (1).

Sample rule descriptions for UDP port 137:

• NETBIOS NS lookup response name overflow attempt
• NETBIOS NS lookup short response attempt
• OS-WINDOWS name query overflow attempt UDP
• ET SCAN Nessus Netbios Scanning

Data Sources

This information is compiled from: IANA Service Name and Transport Protocol Port Number Registry, Emerging Threats Open Ruleset (BSD 2-Clause / GPLv2 per SID range), and Snort Community Rules (GPLv2).