Enhancing Server Security: Mitigating Pass-the-Hash Attacks on Windows Server (2023)


In the ever-evolving landscape of cybersecurity, organizations must stay vigilant against sophisticated threats. Pass-the-hash (PtH) attacks pose a significant risk, allowing attackers to authenticate to remote servers using the NTLM hash of a user's password. Microsoft has been proactive in addressing this threat, and in this article, we explore the advanced security features introduced in Windows Server 2012 R2 to further mitigate PtH attacks.

New Security Features

Protected Users Group

A pivotal addition is the Protected Users group, providing enhanced protection against credential theft. Members of this group on Windows 8.1 devices and Windows Server 2012 R2 hosts benefit from restrictions on credential caching, limiting exposure to plaintext credentials. However, caution is advised when adding highly privileged accounts, as the authentication restrictions are stringent and irreversible.

Authentication Policies

Windows Server 2012 R2 introduces Authentication Policies, offering granular control over authentication settings. Admins can enforce specific conditions, such as restricting NTLM authentication and cipher suite usage. These policies add an extra layer of defense against PtH attacks, especially when applied to high-value accounts.

Authentication Policy Silos

To further fortify security, Authentication Policy Silos enable organizations to isolate workloads and apply tailored authentication policies. By associating user, computer, and service accounts with specific silos, administrators can implement nuanced security measures. Silos are particularly valuable for protecting accounts with administrative privileges, reducing the attack surface.

Configuring Protected Accounts

Requirements for Protected Users

Implementing protected accounts requires adherence to certain best practices. Hosts must run Windows 8.1 or Windows Server 2012 R2 for client-side restrictions, while domain controllers should be at the Windows Server 2012 R2 functional level for domain-side protections. Ensuring AES key availability for members of the Protected Users group is crucial for successful implementation.

Authentication Policies Deployment

Deploying Authentication Policies involves creating policy objects within the Active Directory. These policies specify conditions for TGT lifetime, access control, and other relevant settings. By configuring these policies, organizations can tailor their defenses based on the specific needs and risks associated with different account types.

Troubleshooting and Auditing

To maintain a robust security posture, organizations should actively troubleshoot events related to protected users. New logs, such as the Protected User - Client Log and Protected User Failures - Domain Controller Log, aid in identifying and addressing issues. Additionally, auditing authentication attempts provides valuable insights into the effectiveness of implemented security measures.

Dynamic Access Control and Authentication Policy Silos

Dynamic Access Control Support

For comprehensive security, organizations can leverage Dynamic Access Control (DAC) alongside protected accounts. Enabling DAC involves configuring the Key Distribution Center (KDC) for claims support. This ensures that user claims are recognized and processed, enhancing access controls and overall security.

Authentication Policy Silos Management

Authentication Policy Silos offer a strategic approach to account protection. Admins can create silos to group accounts based on their role or function, applying specific policies to each silo. This granularity is especially beneficial for organizations with diverse security requirements for different account types.


In the relentless pursuit of cybersecurity excellence, Windows Server 2012 R2 provides a robust arsenal against PtH attacks. The combination of the Protected Users group, Authentication Policies, and Authentication Policy Silos empowers organizations to customize their defenses. By understanding the deployment requirements and leveraging the advanced features offered, businesses can elevate their server security, minimizing the risk of credential theft and unauthorized access. Stay ahead of the curve, implement these measures, and fortify your Windows Server environment against evolving cyber threats.

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