One of the most technically demanding tasks is determining the actual effective permissions of a user. Effective permissions do not simply result from what is written in the NTFS ACL, but from the interaction of NTFS permissions, share permissions and Active Directory security groups.

The key principle here is that if NTFS and share permissions apply at the same time, the more restrictive combination always applies. If a user can only read at share level but write at NTFS level, read-only access still applies for network access. This sounds logical, but quickly becomes confusing as soon as several group levels come into play.

This is exactly the case with nested AD groups. A user is a member of a project group, which is a member of a department group, which in turn is in a file server authorization group. What rights does this user have to which folder? This question can only be answered with Windows on-board tools such as the Explorer security tab or icacls with considerable manual effort.

One of the most common mistakes when assigning authorizations: users are entered directly into the ACL instead of controlling access via groups. This saves time in the short term. In the long term, it creates the very orphaned SIDs and lack of transparency that make audits a nightmare.

Microsoft recommends the so-called AGDLP principle for Windows environments: user accounts are included in global groups, these global groups become members of domain-local groups, and only these domain-local groups receive the actual authorizations at folder level. If this model is implemented consistently, a single change to a group structure is sufficient to adjust permissions for all affected users. Direct ACEs, on the other hand, require manual corrections to each individual folder.

Inheritance is actually intended to simplify authorization management: Permissions are set on top-level folders and propagate downwards. This works well as long as the inheritance is not interrupted.

However, broken inheritance on individual subfolders is frequently encountered in practice, often because an admin has quickly created an exception. The result: changes at higher levels no longer take effect, permissions deviate from the rest of the structure in individual places, and no one has a complete overview of which folders actually have their own explicit ACLs.

Employees change departments, take on new projects, temporarily take on substitute roles. Authorizations are assigned for each of these situations. Which rarely happens: The old rights are withdrawn again.

This insidious process is known as access creep or privilege creep. Over time, a user has significantly more access rights than their current role actually requires. This is not only a compliance problem, it is also a concrete security risk. In the event of an attack or an insider incident, these excess rights can be used to cause significantly more damage than necessary.

Explicit Deny ACEs are a frequently underestimated source of errors. They overwrite Allow rights, regardless of the level or group at which the Allow was granted. A user can be a member of several groups, one of which has a deny, without anyone having consciously planned this.

This makes troubleshooting access problems particularly tedious. The classic helpdesk case: A user reports “Access Denied”. Possible causes are missing NTFS read permissions, an overly restrictive share permission, a missing group membership, an interrupted inheritance or a deny ACE somewhere in the chain. This is almost impossible to analyze systematically with on-board tools.

Tools such as the Windows Explorer Security Tab, icacls or PowerShell allow ACLs to be queried. However, they do not provide a structured overview of a large file server with hundreds of folders and nested groups. Group dependencies can hardly be traced, effective authorizations have to be determined manually, and reporting or documentation are simply not scalable with on-board tools.

Especially in audit or security situations, when the question is “Who currently has access to this folder?”, many administrators are faced with a real problem.

All of these problems have a common denominator: A lack of transparency. If you cannot see what is actually in your ACLs, which groups are nested and what effective rights a user really has, you cannot make targeted corrections.

Specialized analysis tools for NTFS permissions start right here. The BAYOOSOFT NTFS Permission Analyzer gives administrators a structured overview of ACL structures, group relationships and effective access rights without having to open each folder manually. For a more comprehensive permission analysis and the ongoing management of access rights, the BAYOOSOFT Access Manager also offers a complete permission concept including recertification and lifecycle management.

Are you unsure about your authorization situation? We will be happy to help you get an overview and give you tips on how to optimize your structures.