5 Reasons to Consolidate Active Directory Domains and Forests

A Windows Server Active Directory (AD) forest is the topmost logical container in an AD configuration. In this article, Michael Otey explains the role forests play in an AD configuration and why it is necessary to consolidate Active Directory forests and domains to improve security and management.

Every Active Directory deployment contains at least one forest, the parent container in the hierarchy. AD forests contain domains, users, computers, Organizational Units (OUs), Group Policy Objects (GPOs), and other objects that represent IT resources.

This article is sponsored by Semperis.

Active Directory is structured in a top-down, logical tree. Businesses can end up with multiple domains and forests due to a variety of historical, organizational, and technical reasons.

However, complex hierarchies with multiple forests and domains can be problematic. Multiple AD forests and domains can have security, operational, and usability concerns that cause organizations to consider consolidating domains and forests.

Let’s take a closer look at the top five reasons why Active Directory consolidation might be the right move for you and how it can improve security, usability, and reduce management requirements.

1.  Complex Active Directory hierarchies increase the AD attack surface

Large organizations may create separate AD domains and forests for different business units. They often have offices or subsidiaries in different geographic locations and set up separate AD domains or forests for each location to optimize network performance.

Likewise, as an organization grows through mergers, acquisitions, or expansion into new regions, it might inherit or create several AD domains and forests to accommodate the different IT infrastructures. In some cases, separate domains or forests are created for technical reasons, such as creating development and testing environments.

However, assaults on identity infrastructure like AD are frequent targets of modern, sophisticated cyberattacks. Complex AD infrastructure, with multiple domains and forests, can have security and visibility gaps that enable hackers to gain access to your infrastructure. This is particularly true for businesses that have undergone multiple AD acquisitions. An organization with multiple domains and forests must secure each one. Multiple domains and forests lead to greater risk of credential theft.

Once your AD infrastructure has been compromised, the theft and misuse of identity credentials make lateral movement across your network possible for hackers. Attackers who gain access to one domain may attempt to steal credentials that can be used in other domains.

Furthermore, a multi-domain or multi-forest environment typically has multiple domain administrators with elevated privileges. If one of these administrative accounts is compromised, it could be used to access restricted resources or to escalate the privileges of other accounts.

2.   Modern Active Directory best practice encourages simpler hierarchies

Early in Active Directory history, domains were thought to be security boundaries, and early deployments involved creating separate domains for different parts of an organization or for different business units. Now, best practice acknowledges that AD domain separation provides an administrative and data replication boundary, but not a true security boundary.

Although domain separation can enhance basic security and administration by isolating sensitive resources, the practice has limitations. AD domains can restrict access to resources within a specific domain, but they do not inherently prevent lateral movement within the network. Attackers who compromise one system in a domain can often leverage that foothold to move laterally to other machines within the same domain. And once attackers have escalated their privileges in one domain, they can easily do the same in every other domain in the forest.

Similarly, having multiple top-level AD forests can increase security challenges and the potential for exploitation. Each forest creates a separate attack surface, and these forests are often connected using trusts. A multi-forest approach does not provide the same level of protection to other forests as a single forest would. If one forest is compromised, the trusts that are in place can expose other forests.

Domain separation adds complexity in managing Group Policy, trust relationships, and access controls. Mistakes lead to security exposures as each domain has different policies, configurations, and auditing requirements. 

Domain separation also limits centralized audit and reporting capabilities. Managing updates and patches across multiple AD domains can lead to delays in deploying critical security updates, increasing exposure to known vulnerabilities.

Trust relationships between separate AD forests can also be complicated and require careful configuration. This complexity makes it challenging to set up secure and efficient cross-forest trust relationships. Reducing the number of AD forests and trust relationships between AD domains and forests lowers your trust-related security risks. A single, well-managed domain or forest results in better security and easier implementation of security policies.

3. Years of configuration drift expose vulnerabilities that attackers exploit

Another reason to consider AD consolidation is to reverse configuration drift. Over time, your AD configuration typically undergoes many changes. Configuration drift occurs when the settings, policies, and configurations within AD domains or forests deviate from their intended or desired state.

This configuration drift causes different AD artifacts to wind up unused, outdated, or otherwise incorrect. In many cases, outdated AD components have ceased to support core business processes and are often overlooked during ongoing operations. And they might expose potential security vulnerabilities that hackers can exploit.

Configuration drift introduces security problems and inconsistent security settings. Some endpoints and servers might have fewer restrictions and safeguards than others, leaving them vulnerable to attack.

Configuration drift can also cause policy conflicts. Differing policies cause unexpected behavior and vulnerabilities, such as allowing the installation and use of software that should be restricted. Consolidating your AD domains and forests can eliminate the configuration drift that has accumulated in an organization.

4. Mergers and acquisitions can lead to security regressions

Most businesses do not have the luxury of greenfield deployments. Instead, they must deal with the coexistence of multiple AD infrastructures from mergers and acquisitions. Past mergers and acquisitions can lead to AD security regressions in several ways. 

Mergers and acquisitions occur because of changing business conditions. However, attempting to integrate different AD environments with divergent security policies and configurations creates confusion and disparities in your organization’s security implementations.

Establishing trusts between AD forests is common, especially following events like mergers and acquisitions, in which access to resources in both entities must be extended. Different organizations may have different security policies, Group Policy Objects, and access controls. Combining these policies leads to inconsistencies and misconfigurations. When these mergers contain legacy AD deployments, with feature limitations or outdated policies, security exposures can occur.

Typically, to enable resource sharing and collaboration, trusts must be implemented between disparate AD environments, which can expose sensitive resources if they are set up incorrectly. In addition, these merged AD systems might not be up to date with the latest security patches and updates. They might contain misconfigurations and privilege escalation vulnerabilities. 

Mergers and acquisitions can also result in user accounts, groups, or computers—and other Active Directory objects—that are orphaned and unmanaged, making them attractive attack targets. Furthermore, employees from merged companies might not be adequately trained or aware of current security best practices and policies, increasing security risks.

Managing these multiple AD forests and domains from acquisitions can be complex and resource intensive. AD consolidation into a single domain or forest results in better security and easier implementation of security policies.

5. Active Directory complexity creates management challenges

Having multiple AD domains and forests in an organization does not just increase security challenges; it also makes managing AD more difficult. Plus, the complexity of configuration creates the potential for misconfiguration.

Complex AD environments have higher operational requirements because you need to manage multiple relationships and trusts. Complex AD hierarchies can also make accessing network resources more difficult for end users.

AD domain separation can hinder collaboration between various parts of the organization. Managing user accounts and credentials separately in different domains is complicated and can lead to inconsistent identity management practices.

Maintaining multiple AD domains and forests is complex and time-consuming. Each forest requires its own set of domain controllers (DCs), administrators, and policies, increasing administrative overhead. Consolidating them simplifies administrative tasks, reduces the number of administrators required, reduces the servers and hardware needed, and makes it easier to manage users, groups, policies, and resources.

Multiple domains and forests can also hinder useability. Consolidating domains and forests can simplify authentication and authorization processes. Users can have a single set of credentials and permissions that apply consistently across the organization. Your personnel can benefit from a more seamless experience when accessing resources within a single, consolidated AD environment. They can also take advantage of single sign-on (SSO) rather than juggling multiple usernames and passwords.

An Active Directory migration tool leads to a smooth and successful outcome

AD forest and domain consolidation enables you to eliminate DCs, reduce the attack surface of your environment, reduce complicated trust environments, and provide improved consistency for security policies. Similarly, consolidation can help trim redundant GPOs, making account and object management efforts easier. Plus, it can improve your user experience by making it easier for employees to access critical resources. 

Note that although the benefits of AD domain and forest migration and consolidation can be significant, the process can be complex. AD migration and consolidation require proper planning and execution to avoid disruptions.

Organizations should conduct a thorough assessment of their specific needs and objectives to ensure a smooth transition of the AD infrastructure. An Active Directory migration tool that includes security considerations can provide guidance that your technical team can use to streamline the migration process while maintaining robust AD protection.

With careful planning and the right tools, consolidation of your AD infrastructure can strengthen your organization’s security posture and simplify identity management.