Active Directory (AD) remains the most targeted asset in enterprise environments. When attackers compromise Tier 0 systems—your identity and security infrastructure—they gain the keys to your entire organization. Domain controllers, public key infrastructure (PKI), federation services, and privileged accounts all become potential weapons in the hands of adversaries who successfully escalate privileges.
Why Tier 0 Protection Demands a Purpose-Built Approach
This guide walks through the process of building a secure Tier 0 administrative environment using Privileged Access Workstations (PAWs). You’ll learn how to identify and classify your most critical assets, enforce strict administrative boundaries, deploy hardened workstations, implement network segmentation, and establish monitoring for credential-based attacks.
Ravenswood Technology Group has helped organizations across regulated industries design and implement modern tiered access models and PAW architectures. Our consultants have deep expertise in Microsoft identity solutions and literally wrote the book on AD security. The strategies outlined here reflect real-world experience protecting complex AD environments from sophisticated threat actors.
Step 1: Identify and Classify All Tier 0 Assets
Before implementing technical controls, you need a complete picture of what you’re protecting. Tier 0 assets are those that provide direct control over your security and identity infrastructure. AD is the preeminent example, but the scope extends well beyond domain controllers.
Map Every Asset that Provides Identity or Security Control
Start by inventorying all systems that can influence your identity plane:
- Active Directory Domain Services (AD DS)
- Active Directory Certificate Services (AD CS/PKI): Certificate authorities that authenticate users, devices, and services
- Microsoft Entra ID Connect: The synchronization engine linking on-premises AD to cloud identity
- Federation services: AD FS, Okta, Ping, or other identity providers that extend trust boundaries
- Privileged Identity Management (PIM) and Just-in-Time (JIT) systems: Tools that govern elevated access requests
- Identity and Access Management (IAM) tooling: Solutions like Microsoft Identity Manager (MIM), SailPoint, and Savyint that automate provisioning
Beyond the obvious identity systems, document implicit Tier 0 dependencies. DNS servers that support AD lookups, DHCP infrastructure, and backup systems that store AD data all influence security posture. If an attacker can manipulate DNS or restore a compromised backup, they’ve effectively gained Tier 0 access through a side channel.
Establish Tier 0 Boundaries and Ownership
Once you’ve mapped your assets, define explicit boundaries. Which accounts, systems, and administrators belong exclusively to this tier? The tiered access model separates environments into three levels:
- Tier 0: Identity and security infrastructure (AD, PKI, Entra ID, IAM systems)
- Tier 1: Servers, applications, and cloud services
- Tier 2: Client computers, user workstations, and related devices
The critical principle is that control flows downward, never upward. A Tier 0 administrator can manage Tier 1 or Tier 2 resources, when necessary, but Tier 1 and Tier 2 administrators must never be able to exert control over Tier 0 assets. This separation prevents privilege escalation attacks where an adversary compromises a lower-tier system and pivots to domain admin access.
Assign clear ownership for each Tier 0 asset and document administrative responsibilities. This clarity becomes essential when implementing technical enforcement and auditing access patterns.
Step 2: Define Strict Administrative Roles and Privileges
With your Tier 0 boundaries established, redesign administrative workflows to enforce least privilege principles throughout the environment.
Redesign Administrative Workflows Using Least Privilege
Domain Admin-level access should be reserved for a small number of essential personnel who perform specific Tier 0 tasks. In many organizations, far too many accounts hold administrative privileges “just in case” or due to legacy practices that predate modern security thinking.
Audit your current privileged accounts and ask hard questions. Does each administrator actually need persistent elevated access? Can their tasks be accomplished with more granular permissions? The goal is to minimize the number of accounts capable of modifying Tier 0 assets and ensure that elevated access is granted only when operationally required.
Introduce role separation to prevent privilege overlap between identity, infrastructure, and server teams. An administrator responsible for managing Exchange servers (Tier 1) should not also hold permissions to modify AD schema or manage domain controllers. When a single account spans multiple tiers, a compromise in the lower tier creates an immediate path to Tier 0.
Adopt Modern Microsoft Privileged Access Models
Microsoft’s enterprise access model provides updated guidance for hybrid environments where on-premises AD coexists with Microsoft Entra ID and cloud workloads. It’s also recommended to employ Just-in-Time (JIT) and Just-Enough-Administration (JEA) principles where appropriate.
With JIT access, administrators request elevated permissions for specific tasks and timeframes. Approvals can be automated or require human review depending on sensitivity. This approach eliminates standing privileges that persist whether or not they’re needed, reducing the window of opportunity for attackers who compromise an admin credential.
Align your workflows with Microsoft’s current tiering guidance, which accounts for both on-premises and cloud control planes. The clean source principle dictates that any user, device, or system capable of controlling a downstream resource becomes a security dependency. Your administrative architecture must account for all these dependencies.
Step 3: Build and Harden Privileged Access Workstations
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If it’s time to take that first step toward leveling up your organization’s security, get in touch with Ravenswood to start the conversation.
PAWs are purpose-built, hardened devices used exclusively for performing administrative tasks against Tier 0 systems. PAWs prevent privileged credentials from being exposed to malware, phishing, or other attack vectors that plague productivity workstations.
Standardize Privileged Access Workstation Configuration Based on Microsoft Security Baselines
PAW devices require hardening that goes well beyond standard endpoint security. Configure workstations using Microsoft security baselines and implement defense-in-depth controls:
- Hardened OS configurations: Disable non-essential services, implement secure boot, and lock down OS profiles
- Attack surface reduction (ASR) rules: Prevent common exploitation techniques at the endpoint
- Application allowlisting: Use App Control for Windows (formerly Windows Defender Application Control [WDAC]) and AppLocker to restrict which applications and drivers can execute
- Credential Guard: Protect credentials stored in memory from theft by malware
Critically, PAWs must not be used for general productivity activities. Disable Internet browsing, email access, and productivity software to eliminate the compromise vectors that threaten standard workstations. PAW users should have the Exchange Online service disabled in their Microsoft 365 license, eliminating phishing attacks against the account used to log on to PAW devices.
PAW users are configured as standard users without local administrator rights. They cannot temporarily elevate privileges or install unauthorized software. All software delivery flows through a trusted managed system like Microsoft Intune.
Isolate Privileged Access Workstations for Exclusive Tier 0 Administration
PAWs should be the only devices permitted to manage Tier 0 assets. Any activity impacting AD, PKI, Entra Connect, or identity governance must originate from a hardened PAW—never from a productivity workstation where the administrator also checks email and browses the web.
Enforce network segmentation so PAWs can communicate only with approved Tier 0 systems. Windows Firewall outbound traffic should be blocked by default, with explicit rules permitting only necessary administrative connections. This isolation prevents data exfiltration and malware communications even if a PAW was somehow compromised.
Some organizations deploy PAWs as physical devices, while others use Azure Virtual Desktop or virtual machines hosted in a secure enclave. Regardless of deployment model, consistent isolation, control, and monitoring remain essential.
Step 4: Implement Strong Authentication Controls on Tier 0 Endpoints
Strengthen authentication requirements for any access to Tier 0 resources:
- Multi-factor authentication (MFA): Require MFA for all administrative access, using hardware tokens or phishing-resistant methods where possible
- Certificate-based authentication or smartcards: Add cryptographic assurance to identity verification
- Authentication policies and silos: Use AD authentication policy silos to restrict where privileged accounts can authenticate
- Kerberos hardening: Disable older encryption types and enforce AES encryption for Kerberos tickets
- NTLM restriction: Disable NTLM where feasible, as it remains vulnerable to pass-the-hash and relay attacks
These controls ensure that even if an attacker obtains a password hash or credential artifact, they face additional barriers before gaining Tier 0 access.
Step 5: Deploy Monitoring and Detection for Tier 0 Security
A secure Tier 0 environment requires continuous monitoring to detect and respond to threats before they succeed. Prevention is essential, but detection and response capabilities provide critical defense-in-depth.
Integrate Microsoft Defender for Identity to Detect Lateral Movement and Credential Attacks
Microsoft Defender for Identity (MDI) is a cloud-based solution purpose-built to detect identity-based attacks against AD environments. Deploy MDI sensors on domain controllers to gain visibility into credential theft attempts, reconnaissance activity, and privilege escalation.
MDI detects attack patterns including:
- Pass-the-Hash (PtH): Attackers reusing captured password hashes to authenticate as privileged users
- Golden Ticket attacks: Forged Kerberos tickets granting persistent domain admin access
- Unusual admin activity: Deviations from normal administrative behavior patterns
- Lateral movement paths: Exposed privilege chains that attackers could exploit
- Legacy protocol usage: Detection of insecure protocols like NTLM and SMBv1
Feed MDI alerts into Microsoft Sentinel or your existing security information and event management (SIEM) / security orchestration, automation, and response (SOAR) platform to enable rapid incident response. When detection systems identify suspicious activity, security teams need immediate visibility and automated response playbooks to contain threats.
Audit, Log, and Verify All Administrative Actions
Enable comprehensive logging for Tier 0 systems:
- AD changes and privileged operations
- Authentication attempts and failures
- Group membership modifications
- Schema and configuration updates
- Administrative console access and PowerShell execution
Log collection is only valuable if logs are analyzed. Establish baselines for normal administrative activity and alert on anomalies. Regular reviews should verify that logging is complete, alerts are tuned appropriately, and detection coverage addresses current threat intelligence.
Organizations often benefit from Active Directory Health Check assessments to validate log completeness and detection maturity. External experts can identify gaps that internal teams may overlook due to familiarity with their own environment.
Step 6: Test, Validate, and Maintain the Tier 0 Environment
Building a secure Tier 0 environment is not a one-time project. Ongoing validation and maintenance ensure that security controls remain effective as threats evolve and organizational changes introduce new risks.
Conduct Periodic Security Reviews and Hands-On Validation
Schedule regular assessments to verify that your Tier 0 protections work as designed:
- Tier 0-focused penetration tests: Engage red teams to simulate adversary attempts at privilege escalation
- Purple team exercises: Collaborative testing where offensive and defensive teams work together to identify gaps
- AD health checks: Comprehensive reviews of configuration, security settings, and operational procedures
Confirm that PAW devices remain hardened and free from administrative drift. Over time, exceptions creep in, such as a temporary internet access rule that becomes permanent, or an additional application is installed for a specific task. Regular audits catch these deviations before they create exploitable weaknesses.
Test your detection capabilities by simulating common attack patterns. Does your MDI deployment detect pass-the-hash attempts? Do alerts trigger appropriate response workflows? Validation testing provides confidence that investments in monitoring actually deliver protection.
Implement Continuous Governance and Operational Upkeep
Security requires ongoing operational discipline:
- Credential rotation: Regularly rotate privileged credentials and service account passwords
- Lifecycle management: Remove access for administrators who change roles or leave the organization
- Baseline updates: Keep PAW configurations, group policies, and OS images aligned with current Microsoft recommendations
- Patch management: Prioritize security updates for Tier 0 systems and PAW devices
Document your Tier 0 environment thoroughly, including asset inventories, administrative procedures, and incident response plans. When security events occur, well-documented environments enable faster investigation and recovery.
How Ravenswood Helps Organizations Build Secure Tier 0 Environments
Implementing a secure Tier 0 environment with PAWs requires specialized expertise in Microsoft identity solutions, AD architecture, and privileged access management. Ravenswood Technology Group brings deep experience from securing complex AD ecosystems across regulated industries.
Provide Deep Architectural and Implementation Expertise
Ravenswood consultants design and deploy comprehensive Tier 0 security solutions:
- Tier 0 isolation: Architectural design that separates identity infrastructure from lower tiers with technical enforcement
- Modern PAW architectures: Purpose-built workstation deployments that follow Microsoft security baselines and Zero Trust principles
- Privileged access workflows: JIT/JEA implementation through Microsoft Entra PIM and AD JIT elevation
- Zero Trust controls: Authentication policies, conditional access, and network segmentation aligned with modern security frameworks
Our team applies real-world knowledge from securing organizations where security and compliance requirements demand rigorous protection of identity systems.
Deliver Ongoing Support, Assessments, and Operational Maturity Improvements
Beyond initial implementation, Ravenswood provides:
- Identify risk reviews: Assessments that identify vulnerabilities and privilege escalation paths in your environment
- AD hardening engagements: Targeted remediation of configuration weaknesses and security gaps
- Detection tuning: Optimization of Microsoft Defender for Identity and SIEM integrations for your specific environment
- Long-term advisory services: Ongoing guidance to sustain and improve your Tier 0 security posture
An Active Directory Health Check provides an excellent starting point for organizations seeking to understand their current risk exposure and develop a roadmap toward secure Tier 0 operations.
Protecting What Matters Most
Your Tier 0 assets—AD, PKI, Entra ID Connect, and related identity infrastructure—represent the foundation of your security architecture. When these systems are compromised, attackers gain the ability to impersonate any user, access any resource, and persist indefinitely in your environment.
Building a secure Tier 0 admin environment with PAWs dramatically reduces the risk of this catastrophic outcome. By isolating privileged credentials to hardened workstations, enforcing strict administrative boundaries, segmenting networks, and deploying continuous monitoring, you create layered defenses that force attackers to overcome multiple barriers.
PAWs combined with modern tiering create a foundation for Zero Trust identity security. Rather than assuming trust based on network location or device type, every administrative action requires verification from a known, hardened, and controlled endpoint.
The investment in Tier 0 protection pays dividends across your entire security program. When identity infrastructure is secure, attackers lose their most valuable escalation paths. Your organization gains confidence that the systems controlling access to everything else remain under your control.
Ready to strengthen your Tier 0 security posture? Contact Ravenswood Technology Group to discuss how we can help assess, design, and implement a PAW strategy tailored to your environment.
