In today’s cybersecurity landscape, properly managing privileged user accounts in Active Directory (AD) is not just a best practice—it’s a critical security imperative. The rise of sophisticated attacks targeting administrative credentials has made the implementation of a robust tier-based administration model essential for organizations of all sizes. This article explores the importance of AD delegation models, demonstrates practical implementation strategies, and introduces powerful automation tools to maintain security hygiene.

Understanding the Active Directory Tiering Model

The Active Directory tiering model, originally developed by Microsoft, provides a structured approach to administrative access that significantly reduces the attack surface and limits the potential impact of credential compromise. This model categorizes administrative accounts and resources into three distinct tiers:

Tier 0: Identity Infrastructure

• Scope: Domain controllers, domain admin accounts, enterprise admin accounts
• Purpose: Controls the core identity infrastructure
• Risk Level: Highest – compromise here affects the entire forest

Tier 1: Server Infrastructure

• Scope: Member servers, server administrators, application administrators
• Purpose: Manages server infrastructure and enterprise applications
• Risk Level: Medium – compromise affects server infrastructure

Tier 2: Workstation Infrastructure

• Scope: Workstations, end-user devices, helpdesk administrators
• Purpose: Manages end-user computing environment
• Risk Level: Lower – compromise affects workstation environment

The fundamental principle is that higher-tier credentials should never be used on lower-tier systems, as this creates a pathway for credential theft and privilege escalation.

Real-World Implementation Challenges

Case Study 1: Healthcare Organization

A mid-sized healthcare organization with 5,000 employees discovered that their domain administrators were using the same accounts for both server management and routine administrative tasks on workstations. This practice created multiple exposure points where Tier 0 credentials could be compromised.

The Challenge: Manual tracking of privileged accounts across different tiers was impossible, leading to:

• Inconsistent group memberships
• Accounts with inappropriate tier assignments
• No visibility into compliance violations

The Solution: Implementing automated privileged user housekeeping to:

• Automatically classify users based on naming conventions
• Ensure proper group memberships
• Disable non-compliant accounts

Case Study 2: Financial Services Firm

A financial services company faced audit findings related to privileged access management. Auditors identified numerous administrative accounts that didn’t follow established naming conventions and weren’t properly categorized.

The Problem:

• 200+ administrative accounts with inconsistent naming
• Manual group membership management prone to errors
• No automated compliance checking

The Resolution: Systematic implementation of tier-based management with automated housekeeping processes.

Introducing the EguibarIT.HousekeepingPS Module

The EguibarIT.HousekeepingPS PowerShell module provides enterprise-grade tools for maintaining Active Directory hygiene, with the Set-PrivilegedUsersHousekeeping function being a cornerstone for tier-based administration.

Key Features of Set-PrivilegedUsersHousekeeping

This function provides automated management of privileged user accounts with the following capabilities:

Automated Classification Logic

The function intelligently classifies users based on:

1. EmployeeType Attribute: Direct tier assignment (T0, T1, T2)
2. Naming Convention: Suffix-based classification (_T0, _T1, _T2)
3. Compliance Checking: Identifies and optionally disables non-compliant accounts

Built-in Safety Features

• Well-Known SID Protection: Automatically excludes critical system accounts (Administrator, krbtgt)
• ShouldProcess Support: Provides -WhatIf capability for testing changes
• Comprehensive Logging: Detailed verbose output for audit trails
• Error Handling: Robust error management with meaningful feedback

Implementation Best Practices

1. Establish Clear Naming Conventions

Implement consistent naming patterns that reflect the tier model:

2. Regular Housekeeping Schedule

Implement automated housekeeping on a regular schedule:

3. Integration with Change Management

Incorporate housekeeping into your change management process:

Security Benefits and Risk Mitigation

Reduced Attack Surface

• Automatic Classification: Ensures accounts are properly categorized
• Non-Standard Account Detection: Identifies accounts that don’t follow security policies
• Automated Remediation: Can disable non-compliant accounts

Improved Compliance Posture

• Audit Trail: Comprehensive logging for compliance reporting
• Consistent Application: Reduces human error in group management
• Policy Enforcement: Automated enforcement of naming conventions

Operational Efficiency

• Time Savings: Eliminates manual group membership management
• Reduced Errors: Automated processes reduce human mistakes
• Scalability: Handles thousands of accounts efficiently

Measuring Success

Key Performance Indicators (KPIs)

1. Compliance Rate: Percentage of accounts following naming conventions
2. Classification Accuracy: Proper tier assignment percentage
3. Remediation Time: Time to address non-compliant accounts
4. Audit Findings: Reduction in audit exceptions

Monitoring and Reporting

Industry Standards and Compliance

The tier-based administration model aligns with several industry frameworks:

• NIST Cybersecurity Framework: Supports the “Protect” function through access control
• ISO 27001: Addresses access control requirements (A.9)
• NIST SP 800-53: Implements AC-2