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Introduction:
In the relentless battle against cyber threats, the principle of least privilege is a cornerstone of defense, yet its implementation often falls short. Privilege escalation remains a primary attack vector, where adversaries, after gaining an initial foothold, systematically hunt for powerful credentials to access critical assets. This article explores the strategic implementation of a Tiering Model, a structured framework for segregating administrative access to contain breaches and protect crown jewel systems from compromise.
Learning Objectives:
- Understand the critical weaknesses in flat administrative networks that attackers exploit.
- Learn the foundational concepts and structure of a Tiering Model for administrative privileges.
- Acquire practical, actionable steps to implement Tier 0, Tier 1, and Tier 2 segregation across Windows and Linux environments.
You Should Know:
- The Attacker’s Playbook: Why Your Current Admin Setup is a Gold Mine
Modern cyberattacks rarely start at the target’s final destination. Attackers follow a path of least resistance, often beginning with a low-privilege user account compromised via phishing. From there, they perform lateral movement, searching for systems where administrative credentials are stored or used. In a flat network without tiering, a credential dumped from a single IT support workstation can grant access to the entire domain, including core controllers, financial databases, and CEO emails. This model turns every minor breach into a potential catastrophe.
Step‑by‑step guide explaining what this does and how to use it.
Step 1: Reconnaissance. An attacker uses a tool like BloodHound on a compromised Windows machine to map all privilege relationships and paths to high-value targets.
Command: `bloodhound-python -d yourdomain.com -u lowpriv_user -p Password123 -c All`
Step 2: Credential Dumping. Using a tool like Mimikatz, the attacker extracts cached credentials or Kerberos tickets from memory.
Command (Mimikatz): `privilege::debug` then `sekurlsa::logonpasswords`
Step 3: Lateral Movement & Privilege Escalation. The harvested credentials, often for a domain admin, are used to access a Domain Controller (Tier 0) via protocols like RDP or WinRM.
Command: `xfreerdp /v:dc01.yourdomain.com /u:domainadmin /p:HarvestedPassword! +auth-only`
- Deconstructing the Tiering Model: Building the Fortress Walls
A Tiering Model is a logical segmentation of your IT environment based on the sensitivity of the assets. It mandates that administrative accounts for a higher tier cannot be used to log on to systems in a lower tier. The standard model consists of three tiers:
Tier 0: The security nucleus. This includes assets that control the identity and access management fabric itself: Active Directory Domain Controllers, Azure AD Connect servers, PKI Root CAs, and the systems used to manage them.
Tier 1: Critical business servers. This tier encompasses application servers, database servers, file servers, and other infrastructure that hosts sensitive business data.
Tier 2: User Workstations and Devices. This is the vast endpoint estate used by standard users and IT support staff for daily tasks.
Step‑by‑step guide explaining what this does and how to use it.
Step 1: Asset Classification. Inventory all systems and accounts, tagging them as T0, T1, or T2. This is the most critical foundational step.
Step 2: Create Dedicated Admin Accounts. For each tier, create separate, dedicated administrative accounts (e.g., t0_admin, t1_sqladmin, t2_helpdesk). Do not allow T0 admin accounts to be used on T1 or T2 systems.
Step 3: Implement Group Policy Objects (GPOs). Use GPOs to enforce logon restrictions. For example, a GPO on T1 servers can restrict RDP and local logon rights to only T1 and T0 admin groups, explicitly denying T2 admin accounts.
- Hardening Tier 0: Protecting the Keys to the Kingdom
Tier 0 is the most critical and must be protected with extreme measures. A breach here equates to a total network compromise. The goal is to create a highly restricted, easily monitored administrative environment.
Step‑by‑step guide explaining what this does and how to use it.
Step 1: Implement Privileged Access Workstations (PAWs). Dedicate hardened physical or virtual machines for T0 administrative work. These PAWs should have no internet access, no email, and run only essential management tools.
Step 2: Enforce Credential Guard. On Windows PAWs and Tier 0 servers, enable Credential Guard to prevent pass-the-hash attacks using virtualization-based security.
PowerShell: `Enable-WindowsOptionalFeature -FeatureName Microsoft-Hyper-V -All -Online` (then reboot and configure via Group Policy)
Step 3: Restrict PowerShell Remoting. Limit which users can establish PowerShell sessions to Tier 0 systems.
Command: Use the `Set-PSSessionConfiguration` cmdlet or a GPO to define allowed users in the `WinRM` settings.
4. Securing Tier 1 Servers: Isolating Critical Workloads
Tier 1 servers host the applications and data that run the business. The objective is to prevent a compromise at the server level from escalating to Tier 0.
Step‑by‑step guide explaining what this does and how to use it.
Step 1: Network Segmentation. Use firewalls or Network Security Groups (NSGs) in the cloud to block direct network traffic from T2 (user workstations) to T1 servers, except for specific application ports.
Step 2: Just-In-Time (JIT) Administration. Implement a Privileged Access Management (PAM) solution that elevates privileges for a short, specific time window instead of granting standing admin access.
Step 3: Linux Hardening with Sudo. On Linux servers in T1, avoid using the root account directly. Instead, configure fine-grained `sudo` access for specific service accounts.
Configuration: Edit `/etc/sudoers.d/t1_admins`
`%t1_admins ALL=(ALL) /bin/systemctl restart nginx, /bin/systemctl status nginx`
5. Managing Tier 2: Controlling the Endpoint Battlefield
User workstations are the most common initial attack vector. While they are the lowest tier, their security is paramount to prevent the attack from starting.
Step‑by‑step guide explaining what this does and how to use it.
Step 1: Standard User Privileges. Ensure all users operate with standard, non-administrative rights by default. Use a solution like LAPS (Local Administrator Password Solution) for unique, rotated local admin passwords on each workstation.
PowerShell (to check LAPS status): `Get-ADComputer -Identity “Workstation01” -Properties ms-Mcs-AdmPwd`
Step 2: Application Control. Implement policies like Windows Defender Application Control (WDAC) to only allow the execution of approved, signed applications, blocking common malware payloads.
Step 3: Secure Admin Tasks. When T2 helpdesk staff need to perform administrative tasks on workstations, they should use their T2 admin accounts, not their standard user accounts, and never use T0/T1 credentials.
What Undercode Say:
- A flat administrative architecture is an open invitation for threat actors to achieve full domain compromise after a single initial breach. The Tiering Model is not a product but a governance strategy that fundamentally alters the attacker’s cost-benefit calculus.
- Implementation is a journey, not a flip-of-a-switch event. Start with a meticulous asset inventory and classification, then begin hardening Tier 0. The most significant security ROI comes from properly segregating and protecting the Tier 0 identity layer.
The Tiering Model represents a paradigm shift from a perimeter-focused defense to an assume-breach mentality. By logically segmenting administrative access, it creates internal barriers that contain lateral movement, dramatically reducing the blast radius of any security incident. While the initial setup requires significant planning and change management, the result is a more resilient and defensible IT environment where not every user login is a potential key to the entire kingdom. This model is a foundational element of a mature Zero Trust architecture.
Prediction:
The future of identity security will see the Tiering Model evolve through deeper integration with AI-driven Identity Threat Detection and Response (ITDR) platforms. These systems will continuously analyze user behavior, access patterns, and privilege usage across tiers, automatically flagging anomalous activity that violates the tiering policy—such as a T2 admin account attempting to query a Tier 0 system. Furthermore, the concept of tiering will expand beyond on-premises Active Directory to holistically govern privileges in hybrid and multi-cloud environments, creating a unified privilege governance layer across SaaS, IaaS, and traditional data centers.
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IT/Security Reporter URL:
Reported By: Henri Van – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
