Using groups for access to shared drives and resources

Why groups should be your default for file access

Direct user permissions don’t scale. Every joiner/mover/leaver becomes a manual hunt across NTFS ACLs, share permissions, DFS targets, and occasionally local groups on file servers. Groups provide:

• Consistency: one membership change updates access everywhere that group is used.
• Auditability: you can answer “who has access?” by enumerating group membership (with nesting rules understood).
• Separation of duties: request/approval workflows manage group membership instead of touching ACLs directly.
• Blast-radius control: you can revoke access instantly by removing a user from a group, without editing the filesystem.
• Standardization: repeatable patterns across shares and departments reduce tribal knowledge.

In mature setups, the permission model becomes boring—in the best way. “Access to a resource” maps to “membership in a group,” and the filesystem becomes an implementation detail rather than a place where identity lives.

The foundational model: map resources to roles, roles to people

A clean way to think about shared resource access is in layers:

1. Resource layer: the share/folder and its permissions (NTFS + share permissions).
2. Access role layer: groups that represent a specific permission set (Read, Modify, Full Control).
3. Identity layer: users (and sometimes other groups) that become members of the access role groups.

If you keep those layers distinct, you avoid the classic “Finance has Modify except some people who have Read but not the contractors…” mess that ends in broken inheritance and invisible denies.

AGDLP / AGUDLP patterns for file shares (and why they still matter)

Microsoft’s long-standing group strategy patterns are still the backbone of scalable file access:

• AGDLP (single domain): Accounts go into Global groups, those go into Domain Local groups, and permissions are assigned to the Domain Local groups.
• AGUDLP (multi-domain / multi-forest): Accounts go into Global groups, those go into Universal groups, those go into Domain Local groups, and permissions are assigned to the Domain Local groups.

The reason this works is that it cleanly separates “who” (global/universal membership aligned to your org) from “what resource” (domain local groups aligned to a share on a specific file server or domain). It also keeps you from assigning permissions directly to broad org groups that later get reused for unrelated purposes (“All Finance” becomes dangerously overloaded).

When to use Global vs Universal vs Domain Local groups

• Global groups: best for grouping users within a domain (department/team/job function). Commonly used for “Finance Analysts,” “HR Payroll,” etc.
• Universal groups: used when membership needs to span domains and you want a single “org role” group to be referenced broadly. Keep membership changes controlled because they have broader replication impact.
• Domain Local groups: best for representing access to a specific resource in a domain. These are typically the groups you put on ACLs.

Design your share access groups like APIs: specific, stable, and boring

A common failure mode is “one group per share” with vague intent (e.g., FinanceShareAccess). Six months later, nobody remembers what “access” means and people start stacking exceptions. Instead, create groups that encode resource + permission level.

A practical naming convention that scales

Pick a convention and stick to it. One effective approach:

• DL_FS1_Finance_RW — Domain Local, File Server 1, Finance share, Read/Write (Modify)
• DL_FS1_Finance_RO — Domain Local, File Server 1, Finance share, Read Only
• DL_FS1_Finance_FC — Domain Local, Full Control (usually restricted to admins/owners)
• G_Finance_Analysts — Global group for a team
• G_Finance_Managers — Global group for managers

Then map team groups into the access groups. For example: G_Finance_Analysts becomes a member of DL_FS1_Finance_RW.

NTFS permissions vs share permissions: keep one simple

Shared drives usually have two permission gates:

• Share permissions (SMB share): evaluated when connecting to the share.
• NTFS permissions (folder/file ACLs): evaluated for everything inside the filesystem.

A common best practice is to keep the share permissions broad and simple (e.g., “Authenticated Users: Full Control” or “Everyone: Full Control” depending on your policy) and enforce real access control using NTFS. The advantage is fewer moving parts and fewer “why can’t I access it?” tickets caused by mismatched layers.

If you prefer the opposite (tight share permissions and simpler NTFS), you can do that too—but pick a standard and apply it consistently across servers and shares, otherwise troubleshooting becomes archaeology.

Folder structure strategy: avoid ACL explosion

Permissions become unmanageable when you try to express every nuance directly on many subfolders. If you can reshape the structure, do it. Patterns that reduce ACL complexity:

• Top-level folders aligned to ownership: e.g., \\FS1\Shared\Finance, \\FS1\Shared\HR.
• Role-based subfolders: separate “Read-only reference” from “Working” areas if needed.
• Project folders with timeboxed membership: create per-project groups that expire or get reviewed.
• Inheritance by default: break inheritance only where you must, and document why.

“Deny” is not a design tool

Deny ACEs are occasionally necessary, but using Deny to patch a bad group model creates hidden complexity. It breaks expectations during troubleshooting, and it’s easy to forget when a user changes role. Prefer designing the folder layout and group mapping so you rarely need Deny.

Handling common scenarios

Scenario 1: Department share with managers needing extra access

You have \\FS1\Finance. Analysts need Modify, managers need Modify plus access to a restricted folder like \\FS1\Finance\Payroll.

• Create DL_FS1_Finance_RW and apply Modify to the Finance root.
• Create DL_FS1_Finance_Payroll_RW and apply Modify only to Payroll.
• Put G_Finance_Analysts into DL_FS1_Finance_RW.
• Put G_Finance_Managers into DL_FS1_Finance_RW and DL_FS1_Finance_Payroll_RW.

No user gets direct ACLs. The “manager extra access” stays explicit and reviewable.

Scenario 2: Cross-department project folder

For \\FS1\Projects\Project-A, members come from multiple teams and change over time.

• Create DL_FS1_ProjectA_RW and assign Modify to the project folder.
• Optionally create DL_FS1_ProjectA_RO for stakeholders who only need read access.
• Add the right team groups (or individual users temporarily) as members.
• Put a review/expiration process on membership (quarterly recertification, end-date, etc.).

If you can avoid adding individual users by creating a project global group (e.g., G_ProjectA_Team) and managing membership there, you’ll keep the ACL layer clean.

Scenario 3: Contractors and external identities

Contractors are where permissions get messy fast, because their lifecycle and governance often differ from employees.

• Keep contractor identities in a distinct OU and apply tighter policies (MFA requirements, logon restrictions, expiration dates where possible).
• Use separate contractor groups (e.g., G_Finance_Contractors) rather than mixing them into the same employee groups, so reviews can be scoped and risk-rated.
• Prefer Read-only access by default; grant Modify only when the business process requires it.

Auditing and “who has access” questions

Auditors and incident responders will ask variations of:

• Who can access this share/folder?
• Why does this user have access?
• When was access granted, and by whom?
• Can we prove access is reviewed periodically?

If access is group-based, your answers are systematic:

1. Enumerate the groups on the ACL (domain local access groups).
2. Expand nested membership (global/universal groups) to users.
3. Trace membership change history (AD auditing / SIEM / change tickets).
4. Show the review cadence (recertification records, group owner attestations).

Without groups, you’re stuck with per-folder ACL archaeology and screenshots.

Enable the right auditing (without drowning in noise)

There are two different audit concerns:

• Membership changes: when someone is added/removed from an access group (governance).
• Resource access: when files are read/modified/deleted (usage and incident forensics).

For access control governance, group membership auditing is often the higher signal starting point. You can alert on changes to high-impact groups (Full Control groups, sensitive share groups) and require approvals. For file access auditing, enable it selectively for sensitive locations to avoid overwhelming storage and analysts.

Operational practices that keep this healthy long-term

Assign ownership to groups, not to folders

Every access group should have a business owner (often the data owner) and a technical owner (IT). The business owner approves membership; IT enforces standards and ensures the group is used correctly on ACLs.

Recertification: access that isn’t reviewed becomes access that isn’t trusted

Shared drives tend to accumulate “ghost access” from role changes and unfinished projects. Put a review cycle on access groups:

• High sensitivity shares: monthly or quarterly review
• General departmental shares: quarterly or semiannual review
• Project groups: review at milestones and close-out

The most important thing is not the cadence—it’s having a repeatable mechanism and evidence trail.

Keep “Full Control” rare and intentional

Most teams do not need Full Control on a share. They need Modify. Full Control includes the ability to change permissions, take ownership, and potentially lock others out. Reserve Full Control for:

• File server administrators
• A tightly controlled data-owner admin group (if justified)
• Break-glass or recovery scenarios with strong monitoring

Common pitfalls (and how to avoid them)

• Pitfall: One mega-group for everything.
  Fix: Use per-resource, per-permission groups. Keep “org role” separate from “resource access.”
• Pitfall: Broken inheritance everywhere.
  Fix: Default to inheritance; only break it at clear boundaries and document why.
• Pitfall: Mixing employees and contractors in the same groups.
  Fix: Separate groups to simplify review and risk controls.
• Pitfall: Deny rules used as band-aids.
  Fix: Redesign folder layout or group model; use Deny only when absolutely necessary.
• Pitfall: Granting access by editing ACLs “just this once.”
  Fix: Make the group workflow the easiest path; treat direct ACL edits as policy violations.
• Pitfall: No lifecycle controls.
  Fix: Add owners, reviews, and (where possible) expirations for project and high-risk access groups.

Practical blueprint: a repeatable build process for a new share

1. Define the resource boundary: What is the share root? Where are the sensitive subfolders?
2. Define access roles: Read-only, Modify, Full Control (and any special-case roles).
3. Create domain local access groups: one per role (RO/RW/FC) with consistent naming.
4. Map org groups into access groups: add global/universal groups as members.
5. Set permissions: apply NTFS permissions to the access groups; standardize share permissions.
6. Document ownership and intent: who approves membership, what the group grants, and what data it protects.
7. Enable auditing for critical groups: alert on membership changes for sensitive shares.
8. Set review cadence: ensure recertification and offboarding processes are aligned.

Hybrid considerations: on-prem shares with cloud identity and governance

Many environments keep file servers on-prem while identity governance moves toward cloud services. The principle still holds: grant access using groups, and manage those groups with strong lifecycle controls. Even if the governance system is modern, the file share is still enforced by SMB + NTFS, so the group strategy is your bridge between modern approvals and legacy enforcement.

Closing: make access predictable

Shared drives become “risky” when access is ad hoc and permissions are scattered. Groups turn access into a predictable system: clear roles, consistent mapping, and a single place to manage change. If you standardize your group patterns (AGDLP/AGUDLP), naming, and review process, you get fewer tickets, cleaner audits, and faster incident response—without needing to constantly redesign your shares.