PCI scan - CIFS NULL Session Permitted

Posted on 2016-11-15
Last Modified: 2016-11-16
Hello - I am currently going through a PCI audit and they found the below vulnerability.

3.1.5. CIFS NULL Session Permitted

The policy "Network access: Named pipes that can be accessed anonymously" has netlogon,samr,lsarpc in the list. I believe this is where the vulnerability came from. I understand they are ldap services but do I need to allow them via anonymous access? is there a more secure method for these services to use?
Question by:agcsupport
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LVL 64

Accepted Solution

btan earned 500 total points
ID: 41889072
Suggest you go to the server and take steps for disabling SMB/NETBIOS NULL Session on domain controllers using group policy.

Network access: Restrict Anonymous access to Named Pipes and Shares
Network access: Do not allow anonymous enumeration of SAM accounts
Network access: Do not allow anonymous enumeration of SAM accounts and shares
Network access: Shares that can be accessed anonymously

Network access: Let Everyone permissions apply to anonymous users
Network access: Allow anonymous SID/Name translation

Also update the registry key values to restrict null session as below:

RestrictAnonymous = 1
Restrict AnonymousSAM = 1
EveryoneIncludesAnonymous = 0

Author Comment

ID: 41889117
@lvl60 - I previously found that article and applied the settings. The below setting allows you to add named pipes basically as an exception. This is where I have the netlogon,samr,lsarpc listed. I did not manually input them so I would have to say they are there by default. These are the services I am wanting to disable if possible. If they are required ldap pipes then I will report them as needed pipes to auditors.

"Network access: Restrict Anonymous access to Named Pipes and Shares"
LVL 64

Expert Comment

ID: 41889236
Those are default named pipes e.g. default list on Windows Server 2003, R2: COMNAP, COMNODE, SQL\QUERY, SPOOLSS, netlogon, lsarpc, samr, browser. There is really no need for these to have anonymous login. User account should authenticated for accountability and audit trail..
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Author Comment

ID: 41889829
So is it your opinion I can remove these entries without issue?

Netlogon - Net Logon service
 Lsarpc - LSA access
 Samr - SAM access
LVL 64

Expert Comment

ID: 41889836
Yes. As MS stated
In operating systems earlier than Windows Server 2003 with Service Pack 1 (SP1), these named pipes were allowed anonymous access by default. In later operating systems, these pipes must be explicitly added if needed.

Author Comment

ID: 41889915
I looked at both of my server 2012 DC's and they have the three named pipes enabled. I also looked on another 2012 server where the policy was set to restrict and there were no services listed. Seems that the domain controllers have them enabled by default which leads me to think they are needed. I suppose I can remove them and see what breaks but not a fan of doing that.

Expert Comment

ID: 41890029
So is it your opinion I can remove these entries without issue?

Id suggest caution here...

Given you understand what dependencies exist in your network which may rely on  this functionality, you are best suited to answer this.  I dont think anyone here, with zero knowledge of what is going on at your company can say you can do this without issue.

That said, the spirit of btan's reply rings true

Author Comment

ID: 41890048
Completely understand nobody here knows my environment and its dependencies. Lets say I set up a 2012 domain test environment. Two DCs and one Win10 workstation with all default settings including the named pipes exceptions. Do I need these services for this environment to work correctly.

Expert Comment

ID: 41890054
You shouldnt with modern versions of the operating system and server roles.  As btan pointed out, this is legacy stuff

Author Comment

ID: 41890079
Thank you everyone for your help - much appreciated.

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