How to reduce attack path via group cleanup

Why group cleanup reduces attack paths

An attack path is a sequence of relationships that lets an attacker move from an initial foothold to a high-value target (like a Tier-0 admin, domain controller access, or control over GPOs/OUs). In most AD environments, the “relationships” that matter are dominated by:

• MemberOf chains (including nested groups)
• Delegated rights granted to groups (OU delegation, GPO rights, object permissions)
• Local admin and remote management rights assigned via groups
• Control of groups (who can modify membership is effectively who can create new paths)

The problem is rarely “a single bad group.” It’s usually sprawl: groups created for one project, reused for another, nested for convenience, and then left unreviewed. If you’ve ever hunted through who has what rights, you’ve seen how permissions and groups become inseparable over time.

Two companion reads that help frame the mechanics behind this: Excess Permissions: Lessons from Legacy Setups and Active Directory Permissions Explained.

Step 1: Inventory groups with transitive visibility (no blind spots)

If you only review “direct members,” you will miss the majority of dangerous paths—because nesting is where privilege hides. Start by collecting:

What to export

• All security groups (scope, type, description, owner if you track it)
• Direct and recursive/transitive membership for each group
• All groups that are:
  • Built-in privileged groups (Domain Admins, Enterprise Admins, Schema Admins, etc.)
  • Granted delegated rights on OUs, GPOs, or critical objects
  • Used to grant local admin rights on servers/workstations

PowerShell starting points (safe read-only)

# 1) List groups with basic metadata
Get-ADGroup -Filter * -Properties GroupScope,GroupCategory,Description,ManagedBy |
  Select-Object Name,SamAccountName,GroupScope,GroupCategory,ManagedBy,Description

# 2) Transitive membership for a known critical group (recursive)
Get-ADGroupMember -Identity "Domain Admins" -Recursive |
  Select-Object ObjectClass,Name,SamAccountName

If nested membership is a recurring pain point in your environment, these two references are directly useful: Active Directory Nested Groups Explained and Auditing Nested Group Memberships: An Expert Guide.

Step 2: Prioritize cleanup by “path impact,” not by aesthetics

Group cleanup fails when it becomes a “make it pretty” exercise. You want to reduce real attacker movement. Prioritize groups that:

1. Shorten the path to Tier-0 (e.g., 1–2 hops to Domain Admin)
2. Create control over identities (reset passwords, write attributes, manage SPNs, add members)
3. Control policy (GPO edit/link, OU delegation, admin rights on management tiers)
4. Are modifiable by too many people (group management delegated loosely)
5. Contain stale identities (inactive users, former employees, old service accounts)

Fast triage buckets

• Tier-0 / forest-impact: groups that touch DCs, AD CS, identity infrastructure, security tooling
• Delegated admin: OU helpdesk groups, workstation admin groups, server admin groups
• Application/service: service accounts and app groups that drift into privileged sets
• Access groups: file shares, apps, and “everyone-ish” memberships (often noisy but high volume)

Step 3: Execute safe group cleanup patterns (that don’t break the business)

Pattern A: Eliminate “privilege by nesting”

A common anti-pattern is nesting broad role groups into privileged groups (or nesting privileged groups into other groups). Fix it by:

• Removing nested groups from privileged groups
• Replacing them with small, explicit admin role groups
• Making membership time-bound (where possible) and owner-approved

Pattern B: Replace “direct user membership” with role groups

Directly adding users to powerful groups is hard to review and easy to forget. Prefer:

• Role group (who the person is / what they do)
• Permission group (what access is granted)
• Then map role → permission with clear change control

Pattern C: Quarantine and stage removals (reduce blast radius)

If you’re unsure whether a membership is still needed, don’t “YOLO delete.” Use a staged process:

1. Move questionable accounts to a quarantine group (or disable and move to a quarantine OU)
2. Set a short validation window (e.g., 7–14 days)
3. Have rollback steps ready (re-add membership, restore group link)

For cleanup governance patterns that translate well to group work, see: Automating inactive user account cleanup: AD & Entra playbook.

Pattern D: Tighten delegated admin groups (OU/GPO rights)

Delegation is necessary—but it’s also how attackers turn “helpdesk-like” access into “domain-like” control. If you have groups with OU-level control or GPO management rights, treat them as attack-path critical.

• Ensure delegated groups are scoped (only the OUs they must manage)
• Ensure permissions are task-specific (not “Full Control because it was easier”)
• Ensure memberships are small and reviewed

Practical delegation hardening: How to delegate OU permissions with minimal risk.

Pattern E: Remove stale members and fix “never reviewed” groups

You’ll usually find:

• Users who changed roles but kept old access
• Contractors who were never removed
• Service accounts added “temporarily” to get something working
• Groups with no description, no owner, and no review history

Cleanup rule that scales: if a group has privileges, it must have an owner and a purpose. If it can’t be explained, it shouldn’t exist (or it should be reduced until it can be explained).

Step 4: Control who can change groups (stop new attack paths from forming)

Cleaning up membership is only half the work. If too many people can add members to powerful groups, the attack paths will regrow.

Minimum control set

• Ownership: every privileged or delegated admin group has an accountable owner (not a generic shared mailbox)
• Change workflow: membership changes require justification and approval (ticket reference)
• Protected delegation: only a small admin group can modify memberships of critical groups
• Audit: alert on membership changes for critical groups

Event IDs to alert on (group membership changes)

• 4728 / 4729: member added/removed (global security group)
• 4732 / 4733: member added/removed (local security group)
• 4756 / 4757: member added/removed (universal security group)

Tip: treat alerts differently for Tier-0 vs. everything else. For Tier-0 groups, you want near real-time alerting and a strict “why did this happen?” loop.

Step 5: Measure the reduction and keep it reduced

If you want “attack path reduction” to be more than a slogan, track metrics that reflect attacker reality:

Metrics that matter

• Count of principals (users/computers/service accounts) with Tier-0 group membership (direct or nested)
• Number of groups that can modify privileged groups
• Transitive membership depth for privileged groups (how many nesting layers exist)
• Privileged group change frequency (and whether each change is justified)

Continuous review cadence

• Weekly: review membership changes in critical groups
• Monthly: review Tier-0 memberships and delegated admin groups
• Quarterly: full transitive membership review + “groups with no owner/purpose” purge

Checklist: group cleanup that actually reduces attack paths

• [ ] Export group inventory + owners + descriptions
• [ ] Generate transitive membership for privileged and delegated groups
• [ ] Identify nested privilege (role groups nested into privileged groups)
• [ ] Stage removals (quarantine + rollback plan)
• [ ] Replace direct user memberships with role groups
• [ ] Tighten who can modify critical groups
• [ ] Turn on alerting for membership changes (Tier-0 first)
• [ ] Re-measure: confirm paths reduced (not just “fewer groups”)

30 / 60 / 90-day execution plan

1. Days 0–30: Inventory + transitive visibility + alerts for Tier-0 membership changes
2. Days 31–60: Remove nested privilege + shrink Tier-0 memberships + owner/purpose enforcement
3. Days 61–90: Delegated admin cleanup (OU/GPO) + local admin group rationalization + quarterly review cadence