Port 137 is associated with NetBIOS Name Service in UDP. This fact sheet explains its role, the risks to be known and the checks that are useful before authorizing or exposing….
What is Port 137 for?…
The port 137/UDP…. is associated with the NetBIOS Name Service, historical resolution and d mechanism, NetBIOS name registration. On former Windows networks, queries can be broadcasted in ’82 or sent to a NBNS/WINS server…. Modern environments are more DNS-based, but devices or applications may still depend on NetBIOS….
Port 137 is linked to NetBIOS 138 and 139 ports, but each has a different role….
Transport Protocol
UDP
Safety precautions
Should we open this port in the firewall?
NetBIOS is an legacy dependency to restrict to segments that still need it. Avoid, expose UDP 137 to the Internet and do not spread the HV NetBIOS between VLANs without need. When a park n, uses more, dependent applications,…. the progressive deactivation of NetBIOS overTip/IP can reduce the surface of the legacy after validation of uses…
How do I check this port?
Windows,…. nbtstat -n displays local NetBIOS names and…. nbtstat -A ADRESSE_IP can query a Life machine when the service is available. To check the network, watch the UDP 137 packages and determine if they are going to go in the year ’82 or to a WINS server….
- To ensure that the application really depends on NetBIOS and not DNS….
- Check the NetBIOS activation on the relevant interface…
- Control WINS if the environment uses one more…
- Compare name resolution with direct access by IP address…
FAQ — port 137 / NetBIOS Name Service….
What is Harbour 137 for in relation to Port 138?….
137 mainly manages NetBIOS names, while 138 transports NetBIOS datagrams. Port 139 concerns NetBIOS sessions….
Why does a NetBIOS name work by IP but not by name?….
The problem may be the NetBIOS resolution, of an hild that does not cross the network, or a WINS server that is missing or misconfigured…
Does DNS still replace NetBIOS?….
In many modern environments yes for current resolution, but some applications or devices may still depend on NetBIOS….