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Port 137 Traffic to Microsoft 365?

Tags: Microsoft, Networking, Security

We are looking to create a default deny policy on our network for both inbound and outbound traffic, and I am seeing a lot of outbound traffic to port 137 on many websites associated with Microsoft 365. Port 137 is of course associated with NetBIOS over TCP/IP, an insecure protocol that we have disabled on our network. I would like to block outbound traffic to port 137 completely, but was not sure if there was a legit reason why our machines would need to send traffic to port 137 on Microsoft websites? I question why Microsft would even have that port open.

Topic

Work with your IT staff. And tell them if this is to be done

In reply to Port 137 Traffic to Microsoft 365?

On each PC, server or router.

Almost every Windows OS has a firewall. Have your IT configure it as you see fit.

Clarification

In reply to Work with your IT staff. And tell them if this is to be done

Thans for the reply, but I am not sure if I was clear in my question. We are not looking to control inbound traffic; we are looking to control outbound traffic to outside websites. What I am asking is whether or not there is a good reason why we would need to allow traffic to be sent to port 137 (associated with NetBIOS over TCP/IP) on websites such as office.live.com?

[kees_b]

Reply To: Port 137 Traffic to Microsoft 365?

In reply to Clarification

Just try and block it on your own PC and see what goes wrong. Then – if needed – contact Microsoft. They seem to have good service for Enterprise customers.

• This reply was modified 4 weeks, 1 day ago by kees_b.

I see this question and possible answers with a quick google.

In reply to Clarification

But that’s not important right now. – Leslie Nelson.

Block it, test the results.

[Author]

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