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Microsoft Defender for Endpoint (MDE) and Defender XDR have introduced significant updates to their Automatic Attack Disruption capabilities, enhancing security for critical infrastructure like Active Directory (AD), DNS, and DHCP servers. These updates enable selective isolation of critical assets, blocking malicious access while allowing essential services to continue running. Additionally, automatic network isolation for unmanaged devices helps prevent lateral movement by attackers.
Key Features:
- Selective Isolation of Critical Assets – Prevents unauthorized access to AD, DNS, and DHCP while maintaining service availability.
- Automatic Containment of Unmanaged Devices – Blocks unmanaged devices from accessing the network, reducing attack surfaces.
- Manual Device Containment – Administrators can manually isolate suspicious devices via the Defender portal.
You Should Know:
To leverage these features, ensure:
- Device Discovery is configured in Standard discovery mode (default).
- The network is marked as monitored.
- Exclude IP ranges that should not be scanned or contained.
Practical Implementation:
1. Verify Device Discovery Settings (PowerShell)
Get-MpComputerStatus | Select-Object -Property DeviceControlDefaultEnforcement, DeviceControlPolicies
2. Configure Network as Monitored (Defender Security Portal)
- Navigate to Settings > Endpoints > Advanced Features > Network Discovery.
- Enable Standard discovery mode.
3. Manually Contain a Device (Defender Portal)
1. Go to Incidents & Alerts.
2. Select the suspicious device.
3. Click Contain Device.
4. Exclude IP Ranges from Scanning
Set-MpPreference -ExclusionIpAddresses "192.168.1.100, 10.0.0.0/24"
Additional Security Measures:
- Monitor Domain Controller Attacks – Attackers often target DCs for ransomware deployment.
- Enable Attack Surface Reduction (ASR) Rules:
Set-MpPreference -AttackSurfaceReductionRules_Ids <RuleID> -AttackSurfaceReductionRules_Actions Enabled
- Audit NTLM & Kerberos Traffic:
auditpol /set /subcategory:"NTLM Authentication" /success:enable /failure:enable
What Undercode Say:
The latest Automatic Attack Disruption enhancements in MDE/Defender XDR provide critical protection against ransomware and lateral movement. By isolating unmanaged devices and securing domain controllers, organizations can mitigate breaches before they escalate.
Key Linux & Windows Commands for Enhanced Security:
Linux: Check network connections (similar to Defender monitoring) ss -tulnp
Windows: Check for suspicious processes
Get-Process | Where-Object { $_.CPU -gt 90 }
Linux: Block an IP via iptables iptables -A INPUT -s 192.168.1.100 -j DROP
Windows: Enable Defender Logging Set-MpPreference -EnableNetworkProtection Enabled
Expected Output:
A hardened security posture with automated attack disruption, controlled network access, and real-time threat containment.
Reference:
References:
Reported By: Nathanmcnulty This – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
