Detections
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18.6.14.1 Ensure 'Hardened UNC Paths' is set to 'Enabled, with 'Require Mutual Authentication', 'Require Integrity', and 'Require Privacy' set for all NETLOGON and SYSVOL shares'

Information

This policy setting configures secure access to Universal Naming Convention (UNC) paths. UNC paths identify network resources using a specific notation. These names consist of three parts: a host device name, a share name, and an optional file path.

The recommended state for this setting is: Enabled, with 'Require Mutual Authentication', 'Require Integrity', and 'Require Privacy' set for all NETLOGON and SYSVOL shares.

In February 2015, Microsoft released a new control mechanism to mitigate a remote code execution vulnerability ( MS15-011 https://technet.microsoft.com/library/security/MS15-011 / MSKB 3000483 https://support.microsoft.com/en-us/kb/3000483 ) in how Group Policy receives and applies connection data when a domain-joined system connects to a domain controller. A threat actor who successfully exploits this vulnerability could take complete control of the affected system. They could then install programs, view, change, or delete data, or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less affected than users who operate with administrative user rights.

MS15-011 https://technet.microsoft.com/library/security/MS15-011 / MSKB 3000483 https://support.microsoft.com/en-us/kb/3000483 requires both the installation of the new security update and also the deployment of specific group policy settings to all computers on the domain from Windows Vista / Server 2008 (non-R2) or newer (the associated security patch to enable this feature was not released for Server 2003). A new group policy template ( NetworkProvider.admx/adml ) was also provided with the security update.

Once the new GPO template is in place, the following are the minimum requirements to remediate the Group Policy security risk:

\\*\NETLOGON RequireMutualAuthentication=1, RequireIntegrity=1, RequirePrivacy=1

\\*\SYSVOL RequireMutualAuthentication=1, RequireIntegrity=1, RequirePrivacy=1

Note: A reboot may be required after the setting is applied to a client machine to access the above paths.

Additional guidance on the deployment of this security setting is available from the Microsoft Premier Field Engineering (PFE) Platforms TechNet Blog here: Guidance on Deployment of MS15-011 and MS15-014 https://techcommunity.microsoft.com/t5/core-infrastructure-and-security/guidance-on-deployment-of-ms15-011-and-ms15-014/ba-p/257759.

Solution

To establish the recommended configuration via GP, set the following UI path to Enabled with the following paths configured, at a minimum:

\\*\NETLOGON RequireMutualAuthentication=1, RequireIntegrity=1, RequirePrivacy=1 \\*\SYSVOL RequireMutualAuthentication=1, RequireIntegrity=1, RequirePrivacy=1

Computer Configuration\Policies\Administrative Templates\Network\Network Provider\Hardened UNC Paths

Note: This Group Policy path does not exist by default. An additional Group Policy template ( NetworkProvider.admx/adml ) is required - it is included with the MS15-011 https://technet.microsoft.com/library/security/MS15-011 / MSKB 3000483 https://support.microsoft.com/en-us/kb/3000483 security update or with the Microsoft Windows 10 RTM (Release 1507) Administrative Templates (or newer).

Impact:

Windows only allows access to the specified UNC paths after fulfilling additional security requirements.

See Also

https://workbench.cisecurity.org/benchmarks/26296

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-8

Plugin: Windows

Control ID: a74ec9c9be14b4e85f77de19e561271e2b1989e06f73a617cdcc3ed0199d526b