138
NetBIOS Datagram
High RiskUDP — System & Infrastructure
Port Overview
Port Number
138
Service Name
NetBIOS Datagram
Transport Protocol
UDP
Category
System & Infrastructure
Security Risk
High
Port Range
Well-Known (0-1023)
What is Port 138?
NetBIOS Datagram Service. Provides connectionless messaging between NetBIOS hosts for browsing, announcements, and other lightweight network operations.
UDP
System & Infrastructure
Commonly Used
Security Considerations
Port 138 (NetBIOS Datagram) is classified as high risk. This port is a common target for automated scanning and brute-force attacks. If you must expose it, restrict access to known IP addresses.
Recommendation: Use firewall rules to whitelist trusted IPs. Enable rate limiting and intrusion detection.