Build a Realistic Endpoint Hardening Baseline

Establishing a robust endpoint hardening baseline is critical for reducing the attack surface of an organization's device fleet. While an exhaustive…

Establishing a robust endpoint hardening baseline is critical for reducing the attack surface of an organization's device fleet. While an exhaustive lockdown might seem ideal, a realistic approach balances security posture with operational usability and administrative overhead. This article outlines a practical strategy for building such a baseline, focusing on Windows environments, leveraging industry best practices, and integrating common management tools.

Our methodology starts with a well-regarded security framework, layers on specific critical controls, and emphasizes systematic testing and documentation to ensure successful implementation across diverse endpoint populations.

Leveraging CIS Benchmarks for Windows Endpoints

The Center for Internet Security (CIS) Benchmarks provide a consensus-driven security configuration guide for various technologies, including Microsoft Windows operating systems. The CIS Microsoft Windows benchmark, specifically Level 1, serves as an excellent foundation for a realistic hardening baseline. Level 1 configurations aim to prevent the most common attack vectors without significantly impacting business functionality.

Key CIS Level 1 Recommendations for Windows 10/11:

Account Policies: Enforce strong password policies (e.g., minimum 14 characters, complexity requirements, history). Lockout policies after a few failed attempts.
Audit Policies: Enable auditing for critical security events (logon/logoff, object access, policy change, etc.) to aid in detection and forensics.
User Rights Assignment: Restrict which users and groups have sensitive privileges (e.g., "Act as part of the operating system," "Debug programs").
Security Options: Configure settings like "Interactive logon: Do not display last user name," "Accounts: Limit local account use of blank passwords to console logon only," "User Account Control: Run all administrators in Admin Approval Mode."
Windows Defender Firewall: Enable the firewall for all profiles (Domain, Private, Public) and configure default inbound/outbound rules to block unnecessary traffic.
Remote Desktop Services: Enforce Network Level Authentication (NLA) and restrict RDP access to authorized groups.

It's crucial to consult the specific CIS Benchmark version relevant to your Windows OS (e.g., CIS Microsoft Windows 11 Benchmark v2.0.0 or CIS Microsoft Windows 10 Benchmark v1.12.0). These documents provide detailed justifications and implementation steps for each recommendation.

Implementation via Group Policy and Intune

Applying these configurations across an enterprise requires centralized management tools. Group Policy Objects (GPOs) are the traditional method for domain-joined Windows machines, while Microsoft Intune's Settings Catalog and Configuration Profiles are essential for modern, cloud-managed endpoints.

Group Policy for Domain-Joined Endpoints:

For on-premise Active Directory environments, create dedicated GPOs for your endpoint baseline. Link these GPOs to Organizational Units (OUs) containing your user and computer objects. Use a structured naming convention, e.g., GPO_Endpoint_Security_Baseline_L1.


# Example: Creating a new GPO and linking it
New-GPO -Name "GPO_Endpoint_Security_Baseline_L1"
New-ADGroup -Name "GP_Endpoint_Security_Admins" -GroupScope Global
Add-ADGroupMember -Identity "GP_Endpoint_Security_Admins" -Members "YourAdminUser"
Set-GPPermissions -Name "GPO_Endpoint_Security_Baseline_L1" -PermissionLevel "GPOEditDeleteModifySecurity" -TargetName "GP_Endpoint_Security_Admins" -TargetType Group
Get-ADOrganizationalUnit -Filter 'Name -eq "Workstations"' | ForEach-Object {
    New-GPLink -Name "GPO_Endpoint_Security_Baseline_L1" -Target $_.DistinguishedName -Enforced No
}

# Key paths for settings within GPMC (gpmc.msc):
# Computer Configuration -> Policies -> Windows Settings -> Security Settings
# Computer Configuration -> Policies -> Administrative Templates

Importing CIS templates (available in LGPO/ADMX format from CIS) can accelerate this process, allowing you to quickly populate GPOs with the recommended settings.

Intune Settings Catalog and Configuration Profiles for Cloud-Managed Endpoints:

For devices managed via Microsoft Intune, leverage the Settings Catalog to configure granular policies. Many CIS recommendations translate directly into settings available in the catalog.

Navigate to Microsoft Intune admin center (endpoint.microsoft.com).
Go to Devices > Configuration profiles > Create profile.
Select Platform: Windows 10 and later, Profile type: Settings catalog.
Give the profile a meaningful name (e.g., "WIN10-11-Endpoint-Baseline-CIS-L1").
In Configuration settings, click Add settings. Search for categories like "Account," "Audit," "User Rights," "Security Options," "Firewall," "Remote Desktop." Select relevant settings and configure them according to the CIS benchmark.
Assign the profile to your device groups (e.g., "All Corporate Windows Devices").

For settings not directly in the Settings Catalog, use custom OMA-URI profiles or PowerShell scripts deployed via Intune.

Critical Security Enhancements Beyond CIS Level 1

While CIS Level 1 is a strong start, several critical security features warrant explicit inclusion in any modern baseline.

Disable SMBv1:

SMBv1 (Server Message Block version 1) is an outdated and insecure protocol known for vulnerabilities (e.g., WannaCry). It should be disabled on all endpoints.


# PowerShell command to disable SMBv1 client (Run as Administrator)
Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol

# PowerShell command to disable SMBv1 server (Run as Administrator)
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters" -Name "SMB1" -Value 0 -Force

This can also be done via Group Policy at Computer Configuration > Policies > Administrative Templates > Network > Lanman Workstation > Enable insecure guest logons (set to Disabled) and Lanman Server > Enable insecure guest logons (set to Disabled) or by deploying a registry key via GPO/Intune.

Enforce LSA Protection:

Local Security Authority (LSA) Protection helps prevent the theft of credentials by protecting the LSA process from unauthorized code injection. It's especially effective against "pass-the-hash" attacks.

Enable this via Group Policy: Computer Configuration > Policies > Administrative Templates > System > LSA > Configure LSASS to run as a protected process. Set it to "Enabled". This typically requires a reboot to take effect.

In Intune, this can be configured via a custom OMA-URI profile:

Name: LSA Protection
OMA-URI: ./Device/Vendor/MSFT/Policy/Config/LocalSecurityAuthority/ConfigureLsaProtection
Data type: Integer
Value: 1

Enable Credential Guard:

Credential Guard uses virtualization-based security to isolate secrets so that only privileged system software can access them. This prevents techniques like "pass-the-hash" and "pass-the-ticket" from working against NTLM hashes and Kerberos Ticket Granting Tickets.

Credential Guard has specific hardware requirements (UEFI firmware, Secure Boot, virtualization extensions, TPM 2.0). Deploy it only to supported machines.

Via Group Policy: Computer Configuration > Policies > Administrative Templates > System > Device Guard > Turn On Virtualization Based Security. Select "Enabled" and configure "Credential Guard" as "Enabled with UEFI lock". UEFI lock prevents remote disablement of Credential Guard. Alternatively, "Enabled without UEFI lock" allows remote disablement but is less secure.

Via Intune: Settings Catalog -> Search for "Virtualization Based Security". Configure "EnableVirtualizationBasedSecurity" and "LsaCfgFlags" (for UEFI lock). If using an Endpoint Security profile, go to "Account Protection" and configure "Credential Guard".

Pilot Testing and Rollout Strategy

Never deploy a new security baseline broadly without rigorous testing. A phased rollout is crucial to identify and mitigate potential operational impacts.

Pilot Group Selection: Identify a diverse group of 25-50 machines representing various departments, hardware configurations, and software installations. Include power users and regular users.
Pilot Duration: Run the pilot for a minimum of two weeks. This allows time for users to encounter common workflows and for issues to surface.
Feedback Mechanism: Establish clear channels for pilot users to report issues (e.g., dedicated helpdesk queue, Teams channel).
Monitoring: Actively monitor pilot machines for security event logs, application crashes, performance degradation, and connectivity issues.
Documentation: Document every issue encountered, its root cause, and the resolution or necessary exception.
Refinement: Based on pilot feedback, adjust the baseline GPOs/Intune profiles. If significant changes are made, consider a smaller, secondary pilot.
Phased Rollout: After successful piloting, roll out the baseline in increasing waves (e.g., 5% of fleet, then 20%, then 50%, then 100%). Monitor closely at each stage.

Documenting Exceptions and Baselines

Detailed documentation is not just good practice; it's a security requirement. For every deviation from the baseline, there must be a documented justification and approval.

What to Document:

Baseline Definition: A clear statement of the chosen CIS benchmark version and any additional controls (SMBv1, LSA, Credential Guard).
GPO/Intune Profile Details: List of applied GPOs, their linked OUs, security filtering, and enforcement status. For Intune, list profile names and assignments.
Specific Settings: A spreadsheet or wiki page detailing each configured setting, its value, and the rationale.
Exceptions: For any setting that deviates from the baseline (e.g., an application requiring SMBv1 on a specific server, a user needing an elevated privilege), document:
- The specific setting and its non-compliant value.
- The business justification for the exception.
- The approval authority for the exception.
- Any compensating controls implemented (e.g., network segmentation, additional monitoring).
- The review date for the exception (exceptions should not be permanent).

Regularly review and update the baseline documentation, especially when operating system versions change, new applications are introduced, or security frameworks evolve.

Common Pitfalls

Over-hardening: Applying too many restrictive policies too quickly can break critical business applications or workflows, leading to user frustration and calls for policy rollbacks. Start with Level 1 and iterate.
Lack of Testing: Skipping or shortening the pilot phase often leads to widespread outages and emergency policy changes.
Ignoring Dependencies: Failing to identify applications or services that rely on deprecated or insecure protocols (e.g., SMBv1) before disabling them. Always scan your environment for such dependencies first.
Inconsistent Enforcement: Having a mix of GPOs and Intune profiles that conflict or don't cover the entire device estate can lead to inconsistent security postures and management headaches.
Insufficient Monitoring: Deploying policies without adequate logging and monitoring in place means you won't detect issues or attacks effectively.
Stale Baselines: Security is not a one-time configuration. Baselines need regular review and updates to keep pace with new threats and evolving best practices.