LDAP over SSL/TLS requirement
Enables LDAP over SSL/TLS on domain controllers. Standard port 636 encrypts all LDAP traffic. Essential for MSPs securing directory queries over untrusted networks.
- Policy path
- Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options
- Supported on
- Windows 10, Windows 11, Windows Server 2016 and later
Enables LDAP over SSL/TLS on domain controllers. Standard port 636 encrypts all LDAP traffic. Essential for MSPs securing directory queries over untrusted networks. Security baselines recommend setting it to 636.
Description
LDAP over SSL/TLS requirement 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 Warning-level policy in the LDAP Signing & Channel Binding category.
Enables LDAP over SSL/TLS on domain controllers. Standard port 636 encrypts all LDAP traffic. Essential for MSPs securing directory queries over untrusted networks.
Microsoft sets the default value to 636 while industry security baselines (CIS, NIST, DISA STIG) recommend 636.
Under the hood, this policy is enforced through the Windows registry at HKLM\System\CurrentControlSet\Services\NTDS\Parameters using the value name LDAPSPortNumber. 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 setting has a meaningful impact on the security posture or operational stability of the system. Leaving it at the Microsoft default is acceptable for standalone or low-risk environments, but most security baselines (CIS, NIST, DISA STIG) explicitly call for hardening it before the device is exposed to untrusted users or networks.
The policy is grouped under LDAP Signing & Channel Binding, 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 ldap signing & channel binding on all domain-joined Windows endpoints.
- Roll out a CIS Benchmark-aligned baseline targeting 'LDAP over SSL/TLS requirement' 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
Leaving this policy at default does not directly grant an attacker access, but it widens the blast radius once initial access is obtained – passwords are easier to guess, lockout doesn't fire, audit trails are incomplete, or lateral movement is quieter. Most regulators and cyber-insurance underwriters now expect this control to be in place at least at the recommended level.
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 – LDAP Signing & Channel Binding) instead of editing Default Domain Policy.
- Navigate to
Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options. - Open LDAP over SSL/TLS requirement and set it to
636. - Click OK and close the editor.
- On the target endpoint, run
gpupdate /force(or wait for the next refresh cycle), then verify withrsop.mscorgpresult /h report.html.
Direct registry path: HKLM\System\CurrentControlSet\Services\NTDS\Parameters\LDAPSPortNumber. You can apply the same change with PowerShell:
New-Item -Path 'HKLM\System\CurrentControlSet\Services\NTDS\Parameters' -Force | Out-Null
Set-ItemProperty -Path 'HKLM\System\CurrentControlSet\Services\NTDS\Parameters' -Name 'LDAPSPortNumber' -Value <value> -Type DWordRegistry mapping
HKLM\System\CurrentControlSet\Services\NTDS\ParametersLDAPSPortNumberREG_DWORD636636