🔍 1. Assess & Inventory First (Don’t Delete Yet)

Start by understanding what you actually have.

What to collect:

• All user accounts
• Computer accounts
• Groups (especially nested ones)
• Domain Controllers
• GPOs (Group Policy Objects)
• OU structure

Tools:

• Native tools like Active Directory Users and Computers
• PowerShell (essential for reporting)
• Optional: PingCastle (great for quick health/security insights)

👉 Focus on reporting only at this stage—no changes.

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🧹 2. Identify Stale & Unused Objects

This is usually the biggest win.

Look for:

• Users not logged in for 90–180+ days
• Disabled accounts that were never deleted
• Computer accounts not active (old machines)
• Service accounts (⚠️ handle carefully)

Example PowerShell:

Search-ADAccount -AccountInactive -UsersOnly -TimeSpan 180.00:00:00

👉 Move these to a “Quarantine OU” instead of deleting immediately.

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🔐 3. Clean Up Groups (Huge Risk Area)

Over 10 years, group sprawl becomes a nightmare.

Actions:

• Identify empty groups
• Find duplicate groups
• Review nested groups
• Validate privileged groups (Domain Admins, etc.)

👉 Document before changing anything.

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🖥️ 4. Review Domain Controllers & Replication

Check:

• Old/decommissioned DCs still in metadata
• Replication health
• FSMO roles

Tools:

• dcdiag
• repadmin

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📜 5. GPO Cleanup (Often Forgotten)

Over time, GPOs pile up and conflict.

Look for:

• Unlinked GPOs
• Duplicate policies
• Legacy settings (XP/2003 era)

Tool:

• Group Policy Management Console

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🗂️ 6. OU Structure Review

Ask:

• Does the OU design still reflect your organization?
• Are permissions delegated properly?

👉 Avoid overcomplicated nesting.

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🔑 7. Service Accounts Audit (Critical)

These are dangerous to touch blindly.

• Identify accounts used by apps/services
• Check:
  • Password expiration settings
  • SPNs
  • Hardcoded credentials

👉 Consider moving toward Managed Service Accounts (gMSA).

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🛡️ 8. Security Baseline Check

Run a security scan:

• Weak password policies
• Kerberos issues
• Delegation risks

👉 Tools like PingCastle or Microsoft Defender for Identity help here.

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⚠️ 9. Implement a Safe Cleanup Process

Never delete directly.

Best practice:

1. Move object → Quarantine OU
2. Disable it
3. Wait 30–60 days
4. Monitor impact
5. Then delete

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🔄 10. Put Maintenance in Place (Most Important)

After cleanup, avoid repeating the problem.

• Monthly stale account review
• Automated scripts (PowerShell)
• Joiner/Mover/Leaver process
• Regular AD health checks

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🚀 Suggested Starting Point (Simple Plan)

If you want a clean starting sequence:

1. Export all users & computers
2. Identify inactive >180 days
3. Create Quarantine OU
4. Move + disable inactive objects
5. Wait & monitor
6. Then proceed to groups and GPOs