Listen to this Post
Introduction
Microsoft has unveiled a game-changing security feature: Microsoft Entra Private Access for Active Directory domain controllers, now in public preview. This innovation bridges a critical gap in hybrid environments by enforcing Conditional Access policies on on-premises resources, including legacy protocols like Kerberos, RDP, and SMB.
Learning Objectives
- Understand how Microsoft Entra Private Access enhances security for domain controllers.
- Learn to configure Conditional Access policies for on-premises resources.
- Explore the dual-layer security architecture (client agent + Private Access Sensor).
You Should Know
1. Enforcing Conditional Access on Kerberos Authentication
Microsoft Entra Private Access intercepts and validates Kerberos requests before granting access to domain controllers.
Key Command (PowerShell):
Register-AzureADPrivateAccessSensor -DCName "DC01" -PolicyId "ca-policy-001"
Steps:
- Install the Private Access Sensor on the domain controller.
- Define a Conditional Access policy in Microsoft Entra ID.
- Use the above PowerShell cmdlet to bind the policy to the DC.
This ensures MFA, device compliance, and risk-based policies apply even for on-premises authentication.
2. Blocking Direct Domain Controller Access
The client-side agent (kernel-mode) blocks unauthorized DC access attempts.
Windows Command (Netsh):
netsh advfirewall set allprofiles state on netsh advfirewall add rule name="Block Direct DC Access" dir=in action=block protocol=TCP localport=88,389,445 remoteip=10.0.0.0/24
Steps:
1. Deploy the agent to endpoints.
- Configure firewall rules to enforce redirection via Entra Private Access.
3. Securing Legacy Protocols (SMB, RDP)
Traditional solutions only protect initial logins, but Entra Private Access secures each resource request.
Example Conditional Access Policy (Azure Portal):
{
"displayName": "Restrict SMB Access",
"conditions": {
"applications": { "includeApplications": ["SMB"] },
"users": { "includeUsers": ["All"] }
},
"grantControls": { "operator": "AND", "controls": ["Require MFA"] }
}
4. Zero Trust for Hybrid Environments
The solution ensures no lateral movement by validating every access attempt.
Linux Command (Test Connectivity):
curl -X POST https://entra-private-access.azure.com/validate -H "Authorization: Bearer $TOKEN"
Steps:
1. Authenticate via Entra ID.
- The sensor validates the token before permitting Kerberos ticket issuance.
5. Handling Internet Outages
Critics raised concerns about dependency on internet connectivity. Microsoft’s architecture includes:
– Cached policies for temporary offline access.
– Fallback modes to ensure DC availability.
PowerShell (Check Sensor Status):
Get-AzureADPrivateAccessSensorStatus -DCName "DC01"
What Undercode Say
- Key Takeaway 1: This is a paradigm shift for securing hybrid environments, closing gaps left by traditional VPNs and perimeter defenses.
- Key Takeaway 2: Critics highlight operational risks (internet dependency), but Microsoft’s fallback mechanisms mitigate downtime concerns.
Analysis:
While revolutionary, organizations must test thoroughly in PoC environments. The solution’s reliance on internet connectivity and kernel-mode agents introduces complexity, but the benefits of Zero Trust for legacy systems outweigh the risks for most enterprises.
Prediction
Within 2–3 years, Microsoft Entra Private Access will become the standard for hybrid AD security, replacing traditional VPNs and direct access methods. As attacks targeting on-premises AD grow, this technology will be critical for mitigating Pass-the-Hash, Golden Ticket, and lateral movement attacks.
References:
IT/Security Reporter URL:
Reported By: Samueleng Microsoft – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
