Block outbound NTLM auth

L3 Networker

Block outbound NTLM auth

With CVE-2018-0950 from Microsoft, if an outlook user clicks on an OLE object in an RTF email, the client will send credentials try to logon. Our security group is quite concerned about this.


While allowing ports 445, 137 and 139 out to the internet is a really bad idea, they want to make sure that it is explicitly blocked. Is the application "ms-netlogon" the app to block? It includes many more ports than just the three mentioned above. Is anyone else doing this? Are 'we' just overreacting?

L6 Presenter

Re: Block outbound NTLM auth

I would think that your firewall policy would already be preventing that application; either by default or exception.


If not, I don't think it would be over-reacting to ensure it's blocked.

L7 Applicator

Re: Block outbound NTLM auth


I would probably just ensure that 445, 137, 139 are blocked to the untrust interface. I wouldn't even do this by app-id unless you need those ports open for something else to function correctly. As @Brandon_Wertz already pointed out, this shouldn't be allowed by your configuration anyways. 

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