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Network access: Shares that can be accessed anonymously

Lists shares accessible via NULL sessions. MSPs keep empty to prevent anonymous data access and discovery.

10 May 20264 min —

Policy path: Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options
Supported on: Windows 10, Windows 11, Windows Server 2016 and later

Lists shares accessible via NULL sessions. MSPs keep empty to prevent anonymous data access and discovery. Security baselines recommend setting it to (empty).

Description

Network access: Shares that can be accessed anonymously is a Windows Group Policy setting located under Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options. It applies to the Computer Configuration branch and is classified as a Critical-level policy in the Network Access & Sharing category.

Lists shares accessible via NULL sessions. MSPs keep empty to prevent anonymous data access and discovery.

Microsoft sets the default value to (empty) while industry security baselines (CIS, NIST, DISA STIG) recommend (empty).

Under the hood, this policy is enforced through the Windows registry at HKLM\System\CurrentControlSet\Services\LanmanServer\Parameters using the value name NullSessionShares. Modifying the value directly through regedit.exe or PowerShell produces the same effect as configuring the GPO, but going through Group Policy is preferred so that the setting is centrally managed and survives reboots, image rebuilds, and policy refresh cycles.

In-depth explanation

This is a critical security control. Misconfiguration creates an exploitable attack path that adversaries actively scan for, and a single overlooked endpoint can compromise the entire fleet. Treat it as a hard baseline requirement rather than an optional tuning knob.

The policy is grouped under Network Access & Sharing, which means it is typically applied through a domain-wide GPO linked at the OU level. In a multi-tenant MSP context, scope it through WMI filters or security group filtering rather than linking at the domain root, so that you can roll out progressively (pilot OU → wider rings → all production).

The setting takes effect after the next Group Policy refresh (gpupdate /force for immediate testing, or by default within ~90 minutes for workstations and ~5 minutes on domain controllers). For computer-side policies a reboot may be required; for user-side policies, a sign-off/sign-on cycle is enough.

Use cases

Apply organization-wide hardening of network access & sharing on all domain-joined Windows endpoints.
Roll out a CIS Benchmark-aligned baseline targeting 'Network access: Shares that can be accessed anonymously' via a dedicated GPO.
Reduce attack surface for accounts that handle privileged credentials or sensitive data.
Standardize the configuration across multiple customer tenants for an MSP-managed fleet.

Security implications

Failing to enforce this policy creates a documented attack path that adversaries actively probe – think Pass-the-Hash, Kerberoasting, NTLM relay, RDP brute-force, LSASS dumping, or token impersonation, depending on the specific control. A single misconfigured endpoint can be enough to pivot to a Domain Admin compromise.

If this policy must remain at default for a legitimate compatibility reason, compensate with a strong detection rule in your EDR/SIEM, isolate the endpoint in its own VLAN, and document the exception with a target remediation date.

How to configure

Open Group Policy Management Console (gpmc.msc) on a domain controller or a workstation with RSAT installed.
Create or edit a GPO linked to the OU containing the target computer configurations. We recommend a dedicated baseline GPO (e.g. SEC – Network Access & Sharing) instead of editing Default Domain Policy.
Navigate to Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options.
Open Network access: Shares that can be accessed anonymously and set it to (empty).
Click OK and close the editor.
On the target endpoint, run gpupdate /force (or wait for the next refresh cycle), then verify with rsop.msc or gpresult /h report.html.

Direct registry path: HKLM\System\CurrentControlSet\Services\LanmanServer\Parameters\NullSessionShares. You can apply the same change with PowerShell:

New-Item -Path 'HKLM\System\CurrentControlSet\Services\LanmanServer\Parameters' -Force | Out-Null
Set-ItemProperty -Path 'HKLM\System\CurrentControlSet\Services\LanmanServer\Parameters' -Name 'NullSessionShares' -Value <value> -Type DWord

Registry mapping

Registry pathHKLM\System\CurrentControlSet\Services\LanmanServer\Parameters

Value nameNullSessionShares

Value typeREG_SZ

Enabled value(empty)

Disabled value(empty)

Frequently asked questions

What does the Network access: Shares that can be accessed anonymously Group Policy do?

Lists shares accessible via NULL sessions. MSPs keep empty to prevent anonymous data access and discovery.

Where do I find this setting in the GPO editor?

Open <code>gpmc.msc</code>, then navigate to <code>Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options</code> and look for <strong>Network access: Shares that can be accessed anonymously</strong>.

What is the Microsoft default value?

<code>(empty)</code> on a fresh Windows install. Domain-joined machines may inherit a different value if a baseline GPO is already in place.

What value do security baselines recommend?

<code>(empty)</code> – aligned with CIS, NIST, and DISA STIG guidance for current Windows versions.

Can I configure this without a GPO?

Yes, by writing to <code>HKLM\System\CurrentControlSet\Services\LanmanServer\Parameters\NullSessionShares</code> directly via <code>regedit</code>, PowerShell, or Intune. A GPO is preferred for centrally managed environments because it survives reimaging and is easier to audit.