Audit Failures filling event log on Windows 7 PCs - Event 5152 - UDP to port 138

Many windows 7 workstations on the LAN have full security event logs. The issue is from many netBIOS broadcasts that are being blocked by the Windows firewall and then logged as an Audit Failure.

Why are all workstations broadcasting to each other so much that the logs are filling?
Is the broadcasting normal behavior?
Will it break the network if I disable or block netBIOS from all workstations? I do use the c$ share remotely.
Possibly the firewall shouldn't be blocking this?

Tons of questions because I want to understand this behavior. Thanks!


The Windows Filtering Platform has blocked a packet.

Application Information:
      Process ID:            4
      Application Name:      System

Network Information:
      Direction:            Inbound
      Source Address:  
      Source Port:            138
      Destination Address:
      Destination Port:            138
      Protocol:            17

Filter Information:
      Filter Run-Time ID:      635422
      Layer Name:            Receive/Accept
      Layer Run-Time ID:      44
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David Johnson, CD, MVPOwnerCommented:
port 138 is the NETBIOS Datagram Service. not blocking this port is the default if you enable file and print sharing

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JohnMan777Author Commented:
The suggestion is to enable the firewall rule that will allow this traffic in. This should be done because it's the default and if we want file sharing and print services to work, it must be self.

I completely disabled NetBIOS on a workstation. I was still able to reach its C Dr. remotely. Also the firewall on the workstation is still blocking 138.

If file sharing works with NetBIOS blocked and disabled, would it be possible to discontinue use of NetBIOS throughout the network?
Seth SimmonsSr. Systems AdministratorCommented:
No comment has been added to this question in more than 21 days, so it is now classified as abandoned.

I have recommended this question be closed as follows:

Accept: David Johnson CD MVP (https:#a42418491)

If you feel this question should be closed differently, post an objection and the moderators will review all objections and close it as they feel fit. If no one objects, this question will be closed automatically the way described above.

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