Why Microsoft Entra ID over On-Premises Active Directory¶

Executive brief for CIOs, CISOs, and identity architects evaluating the migration from on-premises Active Directory to Microsoft Entra ID.

Executive summary¶

Active Directory has been the enterprise identity backbone since Windows 2000. It was designed for a world where users sat behind corporate firewalls, applications ran on domain-joined servers, and network perimeters defined security boundaries. That world no longer exists.

Microsoft Entra ID is the cloud-native identity platform that replaces Active Directory's authentication, authorization, and directory services with a Zero Trust architecture designed for hybrid work, cloud applications, and AI-powered security. This document presents the strategic case for migration --- not as a technology refresh, but as a foundational shift in how identity secures the enterprise.

For CSA-in-a-Box deployments, Entra ID is not optional. Every service in the platform --- Fabric, Databricks, Purview, Azure OpenAI, Power BI, ADLS Gen2 --- authenticates and authorizes through Entra ID. On-premises AD cannot provide the Conditional Access, managed identity, or SCIM provisioning that the platform requires.

1. The Zero Trust mandate¶

The perimeter is gone¶

Traditional Active Directory security assumes that anything inside the corporate network is trusted. This assumption fails when:

• Remote workers authenticate from home networks, coffee shops, and airports
• Cloud applications run outside the corporate firewall
• Contractors and partners need access without domain-joined devices
• Mobile devices cannot join an AD domain
• Lateral movement within the network is the primary attack vector for ransomware

Zero Trust principles in Entra ID¶

Conditional Access --- the policy engine¶

Conditional Access replaces the implicit trust of "you're on the network, so you're trusted" with explicit, signal-based policy evaluation:

IF   user is in "Finance Executives" group
AND  device is NOT compliant (Intune)
AND  location is NOT "Corporate Office" named location
AND  sign-in risk is "Medium" or higher
THEN require phishing-resistant MFA + compliant device
     block access to "Financial Data" apps
     log to Azure Monitor for SOC review

Every authentication to CSA-in-a-Box services --- Fabric workspaces, Databricks notebooks, Purview catalog, Power BI reports --- passes through this policy engine. On-premises AD has no equivalent.

2. Passwordless authentication¶

The password problem¶

Passwords are the single largest attack surface in enterprise identity:

• 80% of breaches involve compromised credentials (Verizon DBIR 2025)
• Password spray attacks against AD are trivial with tools like Hydra and CrackMapExec
• Credential stuffing exploits password reuse across personal and corporate accounts
• Help desk cost for password resets averages $70 per incident (Forrester)

Entra ID passwordless options¶

Federal PIV/CAC integration¶

For federal agencies, Entra ID certificate-based authentication provides native PIV/CAC support:

# Configure Entra ID CBA for PIV/CAC
# Step 1: Upload the issuing CA certificate chain
Connect-MgGraph -Scopes "Policy.ReadWrite.AuthenticationMethod"

$caCert = [System.Convert]::ToBase64String(
    (Get-Content -Path ".\DoD-Root-CA-6.cer" -AsByteStream)
)

New-MgOrganizationCertificateBasedAuthConfiguration `
    -OrganizationId $tenantId `
    -CertificateAuthorities @(
        @{
            Certificate            = $caCert
            IsRootAuthority        = $true
            CertificateRevocationListUrl = "http://crl.disa.mil/crl/DODROOTCA6.crl"
        }
    )

On-premises AD smart card logon requires AD CS, an enrollment agent, and certificate revocation list (CRL) distribution points --- infrastructure that Entra CBA eliminates entirely.

3. Cloud-native management --- eliminate infrastructure¶

What you decommission¶

Operational burden reduction¶

4. Executive Order 14028 and federal compliance¶

EO 14028 requirements¶

Executive Order 14028 (Improving the Nation's Cybersecurity, May 2021) mandates federal agencies to:

1. Adopt Zero Trust architecture --- Entra ID is the Microsoft implementation of the identity pillar
2. Implement multi-factor authentication --- Entra ID MFA with phishing-resistant methods (FIDO2, CBA)
3. Deploy endpoint detection and response --- Entra ID Identity Protection + Defender for Identity
4. Encrypt data in transit and at rest --- Entra ID enforces TLS 1.2+ for all authentication
5. Improve supply chain security --- Entra Workload Identities replace service account passwords

CISA Zero Trust Maturity Model alignment¶

Hard-match hardening --- June/July 2026¶

Microsoft is enforcing hard-match hardening for Entra Connect and Cloud Sync synchronization. This enforcement:

• Prevents soft-matching of on-premises objects to existing cloud objects
• Requires organizations to use explicit hard-match (ImmutableId/SourceAnchor) for all synchronized objects
• Breaks legacy configurations that relied on SMTP proxy address or UPN matching

Organizations still using soft-match synchronization must remediate before the enforcement date. See Hybrid Identity Migration for remediation steps. Failure to remediate will result in duplicate objects and authentication failures.

5. AI and Copilot integration¶

Microsoft Copilot ecosystem¶

Entra ID is the identity layer for the entire Microsoft Copilot ecosystem:

On-premises AD cannot authenticate to any Copilot surface. Migration to Entra ID is a prerequisite for AI adoption.

Security Copilot and identity¶

Microsoft Copilot for Security integrates directly with Entra ID to:

• Investigate risky sign-ins using natural language
• Generate Conditional Access policy recommendations
• Analyze Identity Protection alerts
• Audit PIM role activations
• Query Graph API for identity data

6. Security posture improvement¶

Identity Protection --- ML-powered threat detection¶

Entra ID Identity Protection uses machine learning models trained on 65 trillion daily signals to detect:

Privileged Identity Management (PIM)¶

PIM replaces standing AD admin group membership with just-in-time, time-bound, approval-gated access:

AD model:           User → "Domain Admins" group → permanent 24/7 admin access
Entra PIM model:    User → requests "Global Admin" role → manager approves →
                    access granted for 4 hours → automatic deactivation →
                    full audit trail in Entra audit logs

Attack surface comparison¶

7. Ecosystem and integration advantages¶

Microsoft 365 integration¶

Entra ID is the native identity provider for Microsoft 365. On-premises AD requires AD FS or Entra Connect to bridge this gap. With Entra ID as primary:

• Seamless SSO across all M365 services without federation infrastructure
• Conditional Access applied uniformly to Exchange Online, SharePoint, Teams, and OneDrive
• Sensitivity labels from Microsoft Purview Information Protection bound to Entra identities
• Data Loss Prevention policies enforced based on Entra group membership

Third-party SaaS integration¶

Entra ID has a gallery of 10,000+ pre-integrated SaaS applications with:

• One-click SSO configuration (SAML/OIDC)
• Automatic user provisioning via SCIM
• Conditional Access enforcement
• Application usage analytics

On-premises AD FS requires manual configuration for each application and provides no provisioning or analytics.

Developer platform¶

8. Where on-premises AD still has advantages¶

This assessment is honest. There are scenarios where on-premises AD retains advantages:

These gaps are narrowing with each Entra ID release. For most enterprises, the security and operational benefits of Entra ID outweigh these edge cases.

9. Decision framework¶

Migrate to Entra ID when¶

• Federal Zero Trust mandate (EO 14028) applies to your organization
• You are deploying CSA-in-a-Box or any Azure-native data platform
• Remote/hybrid workforce exceeds 30% of users
• SaaS application portfolio exceeds 20 applications
• Domain controller infrastructure is aging (hardware refresh due)
• AD FS farm requires significant investment to maintain
• Passwordless authentication is a strategic priority
• AI/Copilot adoption is planned

Maintain AD (with hybrid identity) when¶

• Air-gapped or disconnected network segments require local authentication
• Legacy Kerberos applications cannot be remediated within 18 months
• Complex Group Policy estate with 500+ GPOs requires extended migration timeline
• Regulatory requirement for on-premises identity data residency (rare)

The pragmatic path¶

Most organizations do not face a binary choice. The recommended approach is:

1. Deploy hybrid identity immediately (Entra Cloud Sync + PHS)
2. Migrate applications progressively (AD FS relying parties first)
3. Migrate devices progressively (new devices Entra Join, existing via Hybrid Join)
4. Decommission AD infrastructure as dependencies are eliminated
5. Target cloud-only identity as the 18--24 month goal

10. CSA-in-a-Box identity dependency¶

Every CSA-in-a-Box Bicep deployment assumes Entra ID as the identity provider:

// Example: Fabric workspace RBAC bound to Entra group
resource fabricWorkspace 'Microsoft.Fabric/capacities@2023-11-01' = {
  name: workspaceName
  properties: {
    administration: {
      members: [
        entraGroupObjectId  // Entra ID security group
      ]
    }
  }
}

// Example: Databricks SCIM provisioning from Entra ID
resource databricksWorkspace 'Microsoft.Databricks/workspaces@2024-05-01' = {
  name: databricksName
  properties: {
    parameters: {
      enableNoPublicIp: { value: true }
      // SCIM connector syncs Entra users/groups automatically
    }
  }
}

// Example: Key Vault access via Entra RBAC
resource keyVault 'Microsoft.KeyVault/vaults@2023-07-01' = {
  name: keyVaultName
  properties: {
    enableRbacAuthorization: true  // Entra RBAC, not access policies
    tenantId: subscription().tenantId
  }
}

Without Entra ID, none of these integrations function. The identity migration is not a nice-to-have --- it is the prerequisite for platform deployment.

Summary¶

The strategic direction is clear. Entra ID is the identity control plane for the modern enterprise. The question is not whether to migrate, but how fast.

Maintainers: csa-inabox core team Last updated: 2026-04-30