Checklists, criteria and concepts for a secure and efficient AD structure

May 2025
By Thomas Gomell

Introduction

Why a clean Active Directory is crucial

Active Directory (AD) is the backbone of your IT infrastructure. It manages identities, permissions, and policies for users, computers, and services. A well-maintained AD is crucial for your company's security, efficiency, and compliance. However, in reality, AD structures often develop into complex, confusing structures over the years.

The challenge of established structures

Historically evolved ADs often suffer from problems such as stale objects, inconsistent permissions, deep and circular group nesting, or unclear responsibilities. Well-intentioned but excessive structuring often leads to redundancies (e.g., location information in OUs, groups *and* user attributes), which lead to inconsistencies and a loss of trust when changes are made. This "legacy" and unnecessary complexity are not only an administrative nightmare but also pose significant security risks. Standard tools and checklists often only scratch the surface and overlook the deeper structural problems.

This guide: Your guide to optimization

This guide focuses on four critical areas that are essential for a sustainably clean and secure Active Directory:

1. Preparation: The basis for every successful cleanup campaign.
2. Group deletion check: Safely remove unnecessary groups.
3. Naming concepts: Creating clarity and consistency.
4. OU Design & Delegation: Structuring for efficiency and security.

We highlight best practices and provide you with concrete criteria and concepts for optimizing these areas.

More than just a guide: The migRaven expertise

This guide provides valuable insights. For in-depth analysis tailored to your specific environment and implementation support, we recommend our AD auditing serviceOur experts use advanced graph technology to uncover the complex relationships in your AD and develop customized solutions.

Chapter 1: Clean-up Preparation Checklist

The essential basis for a successful AD clean-up

An Active Directory cleanup isn't a project you can complete "on the side." Careful preparation is key to success and prevents unexpected problems or even failures during the process. Before you begin the actual analysis and cleanup, you should ensure that the framework is in place. This checklist will help you cover the most important aspects of preparation.

1. Define goals and scope:

• What should be achieved? Define clear goals for the cleanup project. Is the primary focus on security, performance, compliance, or a combination of these? Should only specific areas (e.g., groups, user accounts) or the entire AD be addressed?
• Scope: Determine which domains, OUs, or object classes should be included in the analysis. Consider dependencies on other systems.

2. Scan configuration & data acquisition:

• Which data is relevant? Make sure that your analysis tool (such as the migRaven.Analyzer) is correctly configured to capture all necessary data. This includes not only standard AD attributes, but also information such as last login (user & computer), password age, group memberships (including nested ones), ACLs on file systems or other resources (if relevant), SIDHistory, adminCount, etc.
• Scan depth: Define how deep group nesting should be analyzed.
• Time planning: Schedule scans so that they place as little strain on the production environment as possible (e.g. at night or on weekends).

3. Ensure necessary access authorizations:

• Analysis account: The service account used for the scan requires sufficient read permissions in Active Directory and, if applicable, on the resources to be scanned (e.g., file servers for ACL analysis). Avoid unnecessarily high permissions (no domain admin!). Document the required permissions precisely.
• Audit logs: Ensure that the necessary AD audit policies are enabled to track changes and that the analytics account has access to the relevant security logs (if required).

4. Definition of namespaces & standards (note minimalism!):

• Check consistency: Analyze existing naming conventions (or lack thereof) for users, groups, computers, and OUs. Inconsistencies complicate analysis and management.
• Target conventions: Define (if not already established) clear and consistent naming conventions for the future that follow the principle of "as little structure as necessary" and primarily describe the function (see Chapter 3). Avoid redundant information in names.

5. Role Owner Definition & Responsibilities:

• Who is responsible? Identify the owners of groups, OUs, and, if applicable, important user accounts (e.g., service accounts). This information is often not maintained.
• Establish process: Establish a process for identifying owners and involving them in the clean-up process (e.g., through comparison with HR data, surveys).
• Decision-making authority: Clarify who is authorized to make decisions about deactivating or deleting objects.

6. Communication & stakeholder engagement:

• Inform: Communicate the clean-up project, its objectives and schedule to all relevant stakeholders (IT department, business units, management, works council).
• Expectation management: Make clear what impacts (positive as well as potentially negative in the short term in the event of errors) the project can have.
• Gather feedback: Involve key stakeholders (e.g., application owners, department heads) to collect information about group or account usage.

7. Technical requirements & tooling:

• Analysis tool: Make sure that the selected analysis tool (e.g. migRaven.Analyzer) is installed, licensed and functional.
• Resources: Ensure sufficient server resources (CPU, RAM, storage) for the analysis tool and the storage of scan data (often in a database).
• Backup & Rollback: Ensure that you have current Active Directory backups and a rollback plan in place in case critical errors occur.

Thorough preparation minimizes risks and ensures your AD cleanup project is efficient and successful. Take the time—it'll pay off!

Chapter 2: Group Concepts & Structural Problems

Courage to leave gaps & understand structure: group concepts and typical problems

Over time, countless groups accumulate in every Active Directory. Many of these are no longer needed (orphaned) or were created for projects long ago. At the same time, uncontrolled growth often results in complex and faulty structures such as circular references or excessively deep nesting. These "legacy issues" and structural problems unnecessarily bloat the AD, increase complexity, impair performance, and can pose significant security risks. Regular auditing, cleanup, and structural improvements are therefore essential. This chapter describes criteria for identifying problematic groups and structures and provides recommendations for dealing with them.

Basic group concepts: types and scopes

Before we delve deeper into problems, a quick overview of the basics:

• Group types:
  • Security Groups: Used to grant permissions. They have a Security ID (SID).
  • Distribution Groups: Used only for email distribution lists and cannot be granted permissions.
• Scopes:
  • Domain Local: Can contain members from any domain, but only receive permissions within their own domain. Ideal for assigning permissions to resources.
  • Global (Global): Can only contain members from their own domain, but can be granted permissions in any domain. Ideal for collecting users with similar roles/functions.
  • Universal (Universal): Can contain members from any domain and have permissions in any domain. Flexible, but changes can replicate the Global Catalog (be careful with frequent changes).

Understanding these types and areas is crucial for the correct implementation of authorization concepts such as AGDLP/AGGP (Account -> Global Group -> Domain Local Group -> Permission), which helps to avoid role misconfigurations.

Identification of problematic groups & structures

In addition to the structural problems already mentioned (circular references, etc.), the identification of orphaned or  non-functional Groups are an important step. Here are the criteria in detail:

• Groups without members: The most obvious indicator: A group without members usually no longer serves any purpose. However, check whether the group is possibly populated dynamically or serves purely as a container group in a complex nesting (rarely useful).
  Tool note: migRaven.Analyzer can easily identify such groups.
• Groups without ACL assignments: If a permission group is no longer listed in the access control lists (ACLs) of any resources (file servers, SharePoint, etc.), it has likely lost its functionality. This requires a scan of the target systems.
  Tool note: migRaven.Analyzer compares groups with the ACLs on file systems.
• Age of the group / Last change: Very old groups whose attributes (e.g. whenChanged) haven't been updated in a long time are often candidates. However, always combine this criterion with others.
• Analysis of group attributes:
  • Description (description): If a description is missing, outdated, or misleading, this indicates a lack of maintenance.
  • Notes (info): Does the notes field contain information about the group's purpose or life cycle?
  • Managed by (managedBy): Is an owner registered? Is this person still in the company or responsible? (See organizational criteria).

Typical structural problems and recommendations

In addition to orphaned groups, there are specific structural problems that frequently occur in established ADs and should be actively addressed:

• Circular group relationships:
  • Problem: Groups are directly or indirectly members of themselves (A -> B -> C -> A). This leads to unpredictable behavior in permission evaluation, performance problems (endless loops during token generation or scripts), and makes permissions extremely difficult to track.
  • ID: Such cycles are difficult to detect with standard AD tools. Graph analysis (such as that performed by migRaven) is essential to uncover the cyclic paths.
  • Suggestion: Circular relationships must be resolved by removing the erroneous membership in the cycle. Define clear nesting rules (e.g., AGDLP/AGGP) and monitor compliance with them.
• Redundant group connections (N:N):
  • Problem: A user or group is a member of a target group in multiple ways (e.g., user A is directly in group Z and also in group Y, which in turn is a member of Z). This unnecessarily increases complexity, bloats Kerberos tokens, and provides no added value.
  • ID: Graph analysis can reveal redundant paths.
  • Suggestion: Clean up redundant memberships. Retain only the direct or logically correct indirect path, according to your role model.
• Deep group nesting:
  • Problem: Groups are nested across multiple levels (e.g., more than 10 levels). This can impair performance during login and permission checks, complicate administration, and significantly reduce clarity.
  • ID: Analysis of the maximum nesting depth for users and groups.
  • Suggestion: Reduce the nesting depth through flattening strategies. Consider whether role or resource groups can be assigned more directly. The goal is a flatter, more understandable structure.
• Groups without ACL assignment (reinforced):
  • Problem: As already mentioned in the deletion candidates, permission groups that are not used anywhere in ACLs are useless. They pose a structural problem because they add unnecessary complexity to AD and are potential sources of error during future changes.
  • ID: Comparison of groups with ACLs on relevant resources (file servers, SharePoint, etc.).
  • Suggestion: After thorough review (see Organizational Criteria), these groups should be deactivated and eventually deleted.
• Role misconfiguration:
  • Problem: Violations of established role concepts such as AGDLP/AGGP (Account – Global Group – Domain Local Group – Permission). Examples: Permission groups become members of role groups, users are placed directly into permission groups or resource groups.
  • ID: Analysis of group memberships and types in the context of the defined role model.
  • Suggestion: Correct the nesting according to the AGDLP/AGGP principle or your defined role model. Assign user roles and role permissions (via Domain Local / Resource Groups).

The systematic identification and resolution of these structural problems is crucial for a stable, secure and high-performance Active Directory.

Organizational criteria & process for cleanup

• Consultation with (potential) owners: Even if technical criteria indicate deletion, consultation is essential. Use the managedByattribute or try to identify the original creator or the department using it. Often, only the business departments know whether a supposedly unused group is still needed (e.g., for rare but critical processes).
• Process: Deactivation before deletion: Don't delete groups immediately. A best practice is:
  1. ID: Mark potential deletion candidates (e.g. by prefix in the name, entry in the description field).
  2. Communication: Inform potential users/owners about the planned deactivation/deletion with a deadline for objections.
  3. Deactivation (simulated): Remove all members from the group, but don't delete the group itself. Alternatively, rename the group (e.g., with a prefix of "_DEACTIVATED_"). Monitor for a defined period of time (e.g., 30-90 days) to see if any issues arise or if users report any issues.
  4. Deletion: If no problems arise, the group can be permanently deleted.
• Documentation: Document every deactivation or deletion decision, including the criteria reviewed, the communication conducted, and the date. This is important for traceability and auditing.
• Define exceptions: Specify which groups should never be automatically deleted (e.g. standard administrative groups, critical system groups).

The combination of technical analyses and a clearly defined organizational process enables effective and secure cleanup of group legacy data in your Active Directory.

Chapter 3: Naming concepts with RegEx

Clarity through consistency: The power of well-thought-out naming conventions

In an established Active Directory, searching for specific objects is often like searching for a needle in a haystack. Inconsistent, cryptic, or simply missing names for groups, users, computers, and OUs not only complicate daily administration, but also automation, reporting, and the enforcement of security policies. Therefore, implementing and consistently adhering to clear naming concepts is a fundamental step toward optimizing your AD.

Why are naming conventions so important?

• Comprehensibility & clarity: Functional names make it immediately clear what an object is responsible for (e.g. a group for access to a specific folder or a role) without relying on redundant information.
• Findability: Structured names allow administrators and scripts to quickly find relevant objects.
• Automation: Consistent names are often a prerequisite for automating processes, e.g. dynamically assigning memberships or policies based on naming patterns.
• Safety: Clear names help avoid misconfigurations (e.g. adding a user to the wrong group) and facilitate audits.
• Delegation: Unique names support the clear demarcation of responsibilities when delegating administrative tasks.

Principle: Minimalism & Clarity

Before you establish conventions, the following principle applies: As little structure as necessary. Avoid encoding information in the name that is already present in other attributes of the object (e.g., the group type or the location if it is in the user attribute). Redundant information leads to inconsistencies and maintenance effort. The name should primarily Other specifications or Purpose of the object clearly communicate.

Best practices for naming conventions:

• Be descriptive: The name should reflect the purpose or function of the object.
• Be consistent: Use consistent patterns, abbreviations and separators.
• Use functional prefixes/suffixes: Clear prefixes should Other specifications or Usage , not the technical type (this is evident from the object properties). Suffixes can, for example, define authorization levels.
• Structure information: Build names logically, e.g. [FunktionsPräfix]_[Bereich/Standort]_[Ressource/Zweck]_[Berechtigungslevel] (Example: FS_Finance_Share_RO).
• Avoid special characters & umlauts: Limit yourself to alphanumeric characters and, if necessary, hyphens or underscores.
• Note length restrictions: In particular sAMAccountName (max. 20 characters).
• Document the convention: Record the agreed naming concept in writing.

Examples of functional prefixes/suffixes:

• Functional prefixes (examples):
  • FS_: File server permissions (e.g. FS_Marketing_Data_RW)
  • APP_: Application access (e.g. APP_SAP_FI_Users)
  • DB_: Database access (e.g. DB_SQL_SalesDB_Reader)
  • PRT_: Printer access (e.g. PRT_BuildingA_Floor2_Color)
  • VPN_: VPN access groups (e.g. VPN_External_Partners)
  • WLAN_: WLAN access groups (e.g. WLAN_Employees)
  • ROLE_: Business roles (e.g. ROLE_Sales_Manager)
  • PROJ_: Project groups (e.g. PROJ_Q3_Campaign_Team)
  • ADMIN_: Delegated administrative tasks (e.g. ADMIN_Helpdesk_UserUnlock)
  • MAIL_: E-mail distribution lists (if security groups are used, e.g. MAIL_All_Employees)
• Permission level suffixes (examples):
  • _RO: Read Only
  • _RW: Read/Write
  • _FC: Full Control
  • _List: List Folder Contents
  • _Admin: Specific admin rights for resource/app
• User prefixes (examples):
  • SVC_: Service Account
  • ADM_: Admin Account (often with suffix for area, e.g. ADM_SQL_Admin)
  • TEMP_: Temporary account

Note: The old prefixes G_, DL_, U_ make  not recommendedbecause they contain redundant technical information.

Validation and search with regular expressions (RegEx):

Regular expressions are a powerful tool for checking compliance with naming conventions and finding objects based on patterns.

• Example RegEx (simplified):
  • Find global groups for finance: ^G_Global_Finance_.*$
  • Finds resource groups with ReadOnly access: ^R_.*_RO$
  • Finds service accounts: ^SVC_.*$
• Application: RegEx can be used in PowerShell, analytics tools, or the AD console to:
  • Find objects that not comply with the Convention.
  • To list objects of a specific type/range.
  • To prepare reports on compliance with the standards.
• Tools: Use online RegEx testers (e.g. regex101.com) to create and test.

The introduction of clear naming concepts requires initial effort, but pays off in the long term through improved clarity, efficiency and security in Active Directory.

Chapter 4: OU Design & Delegation

Structure creates security: Optimal OU design and controlled delegation

The organizational unit (OU) structure in Active Directory is far more than just a visual organizational mechanism. It forms the basis for the targeted application of group policies (GPOs) and the delegation of administrative permissions. A well-thought-out OU design is therefore crucial for the security, manageability, and efficiency of your AD.

Why is OU design important?

• GPO application: Logical structure enables targeted policy application.
• Delegation: Allows the delegation of specific tasks according to the least privilege principle.
• Clarity: Improves orientation for administrators.

Best practices for OU structures:

• Design for purpose (focus on GPO/delegation). Models: Functional, Geographic, Departmental, Hybrid.
• Adequate depth (3-5 levels often good).
• Avoid the standard “Users” and “Computers” containers; move objects to dedicated OUs.
• Pay attention to stability.

Secure delegation of permissions:

• Apply the least privilege principle: grant only minimal rights.
• Use delegation assistants.
• Role-based delegation via dedicated admin groups.
• Understanding and testing inheritance.
• Document and monitor delegation.

Protecting important OUs:

• Enable the “Protect object from accidental deletion” option for all OUs.

A well-thought-out OU design combined with a strict delegation model based on the least-privilege principle reduces the attack surface, improves manageability, and ensures that policies are applied correctly.

---

---

Summary & Next Steps

The path to a healthy Active Directory

Optimizing an existing Active Directory is a continuous task, but focusing on the core areas described in this guide – careful preparation, targeted group cleanup, consistent naming and a well-thought-out OU design with controlled delegation – lays the foundation for a more secure, efficient and easier to manage infrastructure.

Implementing these best practices not only reduces security risks, but also increases the efficiency of administrative processes and improves the traceability of authorizations.

Continuous care is crucial

A one-time cleanup isn't enough. Establish regular processes for reviewing and maintaining your Active Directory to ensure that the achieved order is maintained and new problems are identified early.

Your next step: In-depth analysis with migRaven

This guide provides you with valuable guidance. However, in order to identify the specific weaknesses and optimization potential in of To uncover the unique AD environment, in-depth analysis is essential.

Take advantage of migRaven’s expertise! Our AD auditing service, based on the powerful migRaven.Analyzer for AD and advanced graph technology, provides you with precise insight into the health of your Active Directory within days. We not only identify the symptoms, but also uncover the root causes of structural problems and work with you to develop a customized plan for sustainable cleanup and optimization.