Active Directory (AD) plays a critical role as the primary identity provider for numerous organizations throughout the world, forming the backbone of access control and authentication systems. However, its central role and widespread use makes AD a prime target for attackers seeking to escalate privileges and gain unauthorized access within the target environment. This technique is often known as a domain escalation attack or privilege abuse. These attacks can have devastating consequences, enabling attackers to gain elevated privileges and potentially compromise entire networks.
Although many domain escalation attacks typically involve exploiting misconfigurations or vulnerabilities, some are closely related to poorly managed permissions within the AD infrastructure. The attackers’ goal is to escalate their privileges step by step, often by leveraging legitimate tools and processes within the AD infrastructure. By leveraging these weaknesses and misconfigurations, attackers can gradually elevate their privileges, move laterally across the network, and ultimately gain control over critical systems and data.
Learn more: Simplify AD permissions handling
The tiered delegation model
To mitigate the risks posed by domain escalation attacks, organizations must adopt a proactive approach to securing their Active Directory environments. One effective strategy is to implement a tiered delegation model for Access Control Lists (ACLs)—the backbone of AD’s permission management system.
The tiered delegation model segments administrative privileges into distinct tiers, each with specific roles, access rights, and responsibilities. This approach adheres to the principle of least privilege, ensuring that users and systems have only the minimum necessary permissions to perform their intended functions. For instance:
- Tier 0: Direct access to domain controllers (DCs) and other critical AD infrastructure
- Tier 1: Management of servers and high-privilege applications
- Tier 2: Administration of user accounts with elevated, yet limited, privileges
This structured approach ensures that even if an account is compromised, the potential damage is contained within its designated tier, preventing indiscriminate escalation.
By carefully delegating specific permissions to each tier, organizations can limit the potential impact of a compromised account or insider threat. This approach prevents unauthorized lateral movement and limits the potential damage in case of a successful privilege escalation attack.
Understanding AD ACL permissions
ACLs in AD are used to define the permissions for various objects within the directory. These permissions determine what actions users and groups can perform on AD objects such as user accounts, groups, organizational units, and more.
An ACL contains Access Control Entries (ACEs), each specifying a user’s or group’s permissions. Each ACE specifies a trustee (user or group) and the permissions granted or denied to that trustee for a particular object. Permissions are actions that a user or group can perform on an object. They can be standard permissions (e.g., read, write, delete) or special permissions (e.g., modify permissions, take ownership). Permissions can be inherited from parent objects, making it easier to manage permissions across large AD structures.
How delegation works with AD ACLs
Delegation in AD involves configuring ACLs to assign specific permissions to users or groups for particular tasks. Here’s how it typically works:
- The IT administrator determines the specific administrative tasks that need to be delegated, such as resetting passwords, creating user accounts, or managing group memberships.
- The admin selects the appropriate objects (e.g., OUs, user accounts) on which these tasks will be performed.
- The admin can now configure the ACLs on the objects by using the built-in Delegation of Control Wizard in the Active Directory Users and Computers (ADUC) console, PowerShell specific commands (cmdlets) or scripts, or any valid third-party tool that has that capability.
The challenge of ongoing monitoring and maintenance
Implementing a tiered delegation model is a crucial step. Maintaining and monitoring the underlying ACLs is equally important. However, despite the critical nature of ongoing monitoring and maintenance, these tasks are often tedious and easily overlooked.
The complexity of AD environments and the volume of changes can make manual oversight challenging. Continuous monitoring and maintenance of ACLs involves regularly reviewing and auditing permissions, identifying and remediating misconfigurations, and ensuring that access rights align with the organization’s security policies and operational requirements.
Over time, permissions can become convoluted. Legacy configurations often remain in place, and unintended access rights can creep into the system, creating potential avenues for attackers. For example, a routine ACL audit might find that a former contractor’s account still has extensive permissions within the organization’s AD environment, or that an employee who switched roles within the organization still has permissions assigned to her user account that are no longer needed for her new role. This oversight could enable a malicious insider or an attacker to leverage those privileges for unauthorized activities, such as data exfiltration or system compromise.
This oversight gap can lead to unaddressed vulnerabilities, providing potential avenues for attack, as illustrated by numerous high-profile incidents involving domain escalation attacks and privilege abuse.
Leveraging automated tools for AD security
To address the challenge of continuous ACL monitoring and maintenance, organizations are urged to embrace automation and leverage advanced tools and solutions designed specifically for AD security and governance. These tools can significantly streamline the process of auditing, reporting, and remediating ACL misconfigurations, reducing the workload on IT teams and ensuring consistent enforcement of security policies.
By automating the monitoring and maintenance processes, organizations can proactively identify and address potential vulnerabilities, ensuring that access rights and permissions remain aligned with the organization’s evolving needs and security posture. This continuous improvement approach not only enhances the overall security of the AD environment but also facilitates better alignment with industry best practices and regulatory compliance requirements.
Moreover, automated tools can provide valuable insights and analytics, enabling organizations to identify trends, anomalies, and potential areas of concern within their AD infrastructure. This data-driven approach empowers security teams to make informed decisions, prioritize remediation efforts, and implement targeted security controls to mitigate specific risks.
An ongoing process: securing Active Directory
Securing Active Directory against domain escalation attacks requires a multifaceted approach that combines a tiered delegation model for ACL management with continuous monitoring and maintenance. Securing AD is not a one-time effort but an ongoing process that requires vigilance, dedication, and the adoption of automated tools and processes.
By prioritizing AD security and embracing best practices, organizations can streamline the process of identifying and remediating ACL misconfigurations, significantly reducing their attack surface and protecting their critical infrastructure from malicious actors seeking to exploit privileged access.
This proactive approach not only enhances the overall security posture but also fosters a culture of continuous improvement, enabling organizations to stay ahead of emerging threats and protect their critical infrastructure from malicious actors seeking to exploit privileged access.
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