Mapping legacy AD groups to Entra roles

Start with the right mental model: groups vs roles

In on-prem AD, groups are a universal primitive: they can grant file share access, apply GPO filtering, and represent admin power through delegation and privileged group membership. If you need a refresher on how AD group objects behave (scope, nesting, and why they become hard to reason about), review Active Directory Group Object Management.

In Entra ID, think in two layers:

• Directory roles (Entra roles): rights to manage identity-layer objects (users, groups, apps, auth methods). See Role-based access control in Microsoft Entra.
• Resource roles (Azure RBAC): rights to manage Azure resources (subscriptions, resource groups, Key Vault, etc.). (Often administered alongside directory roles, but scoped differently.)

The key mapping principle is simple: AD groups represent “who” (membership); Entra roles represent “what they can do” (permissions). Your job is to preserve intent while tightening scope and governance.

Step 1: Inventory legacy groups like an investigator, not a janitor

Before you map anything, you need an accurate picture of effective membership and privilege. Legacy AD environments frequently hide power inside nesting chains. Use your existing nested membership audit approach (and improve it if needed) as described in Auditing Nested Group Memberships.

Minimum inventory fields

• Group name + description (what it claims to do)
• Owners / managers (who changes membership)
• Direct members + transitive members (who effectively gets access)
• Where it’s used (ACLs, delegation, apps, scheduled tasks, “tribal knowledge”)
• Privilege level (Tier-0 / identity admin / app admin / operational)
• Change frequency (daily churn vs rare exceptions)

Output matters: you want a mapping worksheet you can hand to security and operations for review and sign-off.

Step 2: Classify groups by intent (so you don’t map names blindly)

Most legacy “admin” groups fall into predictable intent buckets. Classify first, then map:

• Identity operations: password resets, user provisioning, group management, authentication method resets
• Directory governance: role assignment, policy administration, privileged access workflows
• App administration: managing enterprise apps, app registrations, SSO configurations
• Azure resource operations: subscription/resource group ownership, contributor patterns
• Legacy “god groups”: broad, ambiguous access that grew over time (“IT-Admins-All”)

This step prevents the most common failure mode: mapping a group to a powerful role just because the name sounds “admin-ish.”

Step 3: Choose your Entra target primitives

In Entra, you typically implement admin access using a combination of:

• Role-assignable groups to assign directory roles to a group (instead of individuals)
• Privileged Identity Management (PIM) to convert standing privilege into just-in-time activation (see Azure AD PIM: How to manage privileged access to resources)
• Administrative Units to scope “admin rights” to subsets of users/groups/devices (where applicable)
• Access reviews to force periodic re-justification (especially for privileged groups)

Important constraint you must design around

Microsoft Entra directory roles cannot be assigned to on-premises AD groups (synced groups). In practice, that means: you’ll create a cloud role-assignable group in Entra for role assignment, and then decide how to manage its membership (manual, automated, governed, or bridged from your legacy process).

Step 4: Build a mapping matrix (the “translation contract”)

A mapping matrix turns a risky migration into a controlled change. Here’s a template you can copy into your internal worksheet:

The worksheet is also where you “split” legacy groups that bundle multiple jobs into one. That split is usually where you gain the biggest security win with the least operational pain.

Step 5: Pick an implementation pattern (hybrid realities included)

Pattern A: Shadow groups (most common, least risky)

Keep the legacy AD group for on-prem usage (ACLs, legacy apps). Create a cloud role-assignable group for Entra role assignments. Then align membership changes via your joiner/mover/leaver workflow.

• Pros: minimal disruption, clean separation between on-prem and cloud privilege
• Cons: you must ensure membership stays consistent across both worlds (automation helps)

Pattern B: Entra-governed membership (modern governance-first)

Make Entra the membership “control plane,” using PIM + access reviews. Where you still need on-prem groups for apps, you selectively bridge with supported writeback/provisioning approaches.

• Pros: strongest governance, clear auditability
• Cons: higher change impact; requires mature operational readiness

Pattern C: Decompose by scope (stop using one group for everything)

Break a broad legacy group into multiple smaller role-assignable groups and apply scoping (Administrative Units, app scoping, Azure RBAC scope) so “admin” doesn’t mean “admin everywhere.”

How to create a role-assignable group and map it to a role (practical workflow)

This is the operational “happy path” you should standardize:

1. Create a new role-assignable security group in Entra (cloud-only)
2. Assign the required Entra role(s) to the group
3. Add users (preferably through governed workflow)
4. Enable PIM so membership or role activation is time-bound
5. Run access reviews and audit role assignment changes

If you’re still building your Entra identity operations foundation, the broader context in Manage Identities in Microsoft Entra ID pairs well with this mapping work.

Automation note (recommended)

Even if you don’t fully automate role assignment on day one, you should automate reporting immediately: export role assignments, group membership, and PIM eligibility into a daily/weekly snapshot so you can detect drift.

# Example (conceptual): Use Microsoft Graph PowerShell to create a role-assignable group
# and then assign a directory role to it. (Exact commands depend on your tenant setup and permissions.)

Connect-MgGraph -Scopes "Group.ReadWrite.All","RoleManagement.ReadWrite.Directory"

# Create role-assignable group (cloud-only)
$group = New-MgGroup `
  -DisplayName "ENTRA-ROLE-Helpdesk-Admins" `
  -Description "Helpdesk role assignment group (JIT via PIM recommended)" `
  -MailEnabled:$false -SecurityEnabled `
  -MailNickName "entrarolehelpdeskadmins" `
  -IsAssignableToRole:$true

# Next: assign the desired Entra role to the group (role definition lookup + assignment)
# (Implement as a controlled change with review/approval.)
    

Operational guardrails that prevent “cloud Domain Admins”

1) Default to eligible access, not permanent access

Treat privileged roles like production database access: time-bound, logged, and ideally approved. PIM is how you make that practical at scale.

2) Keep role-assignable groups boring and controlled

• Use assigned membership (not dynamic)
• Do not nest groups into role-assignable groups
• Use tight ownership and audited change paths

3) Split “can manage access” from “can use access”

A common legacy mistake is letting the same people both approve and grant themselves access. In Entra, keep clean separation: approvers, group owners, and role-eligible users should be governed explicitly.

4) Validate outcomes with effective-access checks

After every migration wave, verify:

• Who has the role directly vs via group
• Who is eligible vs permanently active
• Which legacy groups are now redundant (and safe to retire)

Common mapping pitfalls (and how to avoid them)

• Mapping by name instead of intent: “GG-Admins” might be helpdesk in one region and full identity admin in another. Always classify intent first.
• Ignoring nesting: nested memberships silently expand privilege. Audit transitive membership before mapping.
• Overusing Global Administrator: it becomes the new “Domain Admins.” Prefer narrower roles and scoped administration.
• Standing privilege for convenience: use PIM to preserve convenience without permanent risk.
• Not documenting scope: role + scope + justification is your defensible security story in audits.

Recommended “migration wave” plan

1. Wave 1 (Low risk): helpdesk-style roles (password reset, user read, basic group tasks) with PIM
2. Wave 2 (Medium risk): application administration roles, scoped where possible
3. Wave 3 (High risk): tenant-wide roles and break-glass architecture refinements
4. Wave 4 (Cleanup): retire or repurpose legacy groups once usage is proven redundant