MDE for Non‑Persistent VDI — Implementation Guide & Best Practices.
1. Overview: Microsoft Defender for Endpoint (MDE) for Non‑Persistent VDI Non‑persistent VDI instances are reset or reprovisioned frequently. To ensure immediate protection and clean device inventory, MDE provides a dedicated onboarding path that calculates a persistent device ID and onboard early in the boot process. Key considerations: Use the VDI onboarding package and choose the single‑entry method (recommended) to avoid duplicate devices when hosts are recreated with the same name. Place the onboarding script in the golden image but ensure it executes only on child VMs (first boot) after the final hostname is assigned and the last reboot completes. Never fully onboard or boot the golden/template/replica image into production; if it happens, offboard and clean registry artifacts before resealing. Consider enabling the portal feature “Hide potential duplicate device records” to reduce inventory noise during transition periods. 2. Stage the scripts in the Golden Image (do NOT onboard the image) Goal: Ensure early, reliable onboarding of pooled VDI instances without tattooing the master image. Download the Windows onboarding package (Deployment method: VDI onboarding scripts for non‑persistent endpoints). Extract and copy the files to: C\Windows\System32\GroupPolicy\Machine\Scripts\Startup Configure Local/Domain GPO to run the PowerShell script at startup (SYSTEM, highest privileges). For single‑entry, add Onboard-NonPersistentMachine.ps1 on the PowerShell Scripts tab. Ensure the script runs only after final hostname and the last reboot in your provisioning flow to prevent duplicate objects. Example (Domain GPO scheduled task at startup as SYSTEM): Program/Script: C\Windows\System32\WindowsPowerShell\v1.0\powershell.exe Arguments: -ExecutionPolicy Bypass -File \srvshare\onboard\Onboard-NonPersistentMachine.ps1 3. Never Onboard the Golden/Template/Replica VM If the golden image was accidentally onboarded (Sense service started), you must offboard and clean before resealing: sc query sense del "C:\ProgramData\Microsoft\Windows Defender Advanced Threat Protection\Cyber\*.*" /f /s /q reg delete "HKLM\SOFTWARE\Microsoft\Windows Advanced Threat Protection" /v senseGuid /f Run the official offboarding script for your tenant before cleanup, when available. 4. (Optional) Tag Devices Automatically from the Image Tags simplify scoping of device groups and policies. Add a DeviceTagging registry value during image build: reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows Advanced Threat Protection\DeviceTagging" /v Group /t REG_SZ /d "VDI-NonPersistent" /f Tag appears after device info refresh; a reboot accelerates reporting. 5. Performance & AV Configuration for VDI (Important) 5.1 Shared Security Intelligence & Cache Maintenance Purpose: Reduce CPU and disk spikes at sign‑in by offloading unpackaging of definitions to a shared source and by pre‑running cache maintenance on the master image. Step‑by‑step GPO configuration: Create a secure UNC share for definition packages (e.g., \srvshare\WDAV-Update) and grant read to VDI computer accounts. GPO → Computer Configuration → Administrative Templates → Windows Components → Microsoft Defender Antivirus → Security Intelligence Updates → Enable “Define security intelligence location for VDI clients” and set \srvshare\WDAV-Update. In the same node, set update cadence (daily time) and enable randomization to avoid I/O storms. PowerShell examples: Set-MpPreference -SignatureUpdateInterval 4 Set-MpPreference -SignatureFallbackOrder "InternalDefinitionUpdateServer|MicrosoftUpdateServer" Run Windows Defender Cache Maintenance on the golden image before sealing: schtasks /Run /TN "\Microsoft\Windows\Windows Defender\Windows Defender Cache Maintenance" 5.2 FSLogix Exclusions Why exclusions matter: FSLogix mounts user profiles as VHD/VHDX files. Scanning these at attach/detach causes logon delays, black screens, and app launch slowness. Paths and extensions to exclude: %TEMP%\*.VHD %TEMP%\*.VHDX %Windir%\TEMP\*.VHD %Windir%\TEMP\*.VHDX \\<storage>\<share>\*.VHD \\<storage>\<share>\*.VHDX \\<storage>\<share>\*.VHD.lock \\<storage>\<share>\*.VHD.meta \\<storage>\<share>\*.VHD.metadata \\<storage>\<share>\*.VHDX.lock \\<storage>\<share>\*.VHDX.meta \\<storage>\<share>\*.VHDX.metadata GPO: Computer Configuration → Administrative Templates → Windows Components → Microsoft Defender Antivirus → Exclusions (File/Folder and Extension). PowerShell examples: Add-MpPreference -ExclusionExtension VHD,VHDX Add-MpPreference -ExclusionPath "C:\ProgramData\FSLogix","\\storage\fslogix-share\*.VHD*" 5.3 General Scan Posture Real‑time & cloud‑delivered protection (GPO): Enable Real‑time protection, Cloud‑delivered protection, Join MAPS, and “Block at first sight.” Scheduled scans (GPO): Daily Quick Scan (e.g., 02:00) with randomization window. Weekly Full Scan (e.g., Sunday 03:00). Consider “Start the scheduled scan only when computer is on but not in use” to reduce user impact. CPU throttling settings: Set-MpPreference -ScanAvgCPULoadFactor 30 # 5..100 (0 = no throttling) Additional scheduling/throttling options (Intune/Policy CSP as applicable): ScanOnlyIfIdleEnabled = True DisableCpuThrottleOnIdleScans = True ThrottleForScheduledScanOnly = True EnableLowCPUPriority = True Validation commands: Get-MpPreference | fl ScanAvgCPULoadFactor,ScanScheduleQuickScanTime,SignatureUpdateInterval Get-MpComputerStatus | fl AMServiceEnabled,AntivirusSignatureVersion,RealTimeProtectionEnabled 6. Validate Onboarding After first boot of a pooled VM, verify device appears in Defender portal (Assets → Devices). For single‑entry method, reboot/redeploy a few instances with the same hostname and confirm one device object is reused. Optionally enable “Hide potential duplicate device records” (Settings → Endpoints → Advanced features). This is like only filtering the view of Devices list does actual remove the records from the MDE portal. Run a detection test if needed (per Microsoft guidance) to verify sensor connectivity. 7. Quick Checklist — Build Step Download VDI onboarding package from Defender portal. Copy scripts to Startup folder in golden image; configure GPO/Task to run PS1 at boot as SYSTEM. Do NOT onboard/boot the golden image into production; if it happens, offboard + clean senseGuid & Cyber cache. (Optional) Set DeviceTagging registry value for scoping (e.g., VDI-NonPersistent). Configure Shared Security Intelligence path; schedule updates; run Cache Maintenance on master image. Apply FSLogix AV exclusions (paths + extensions). Set scan posture (RTP + cloud, schedules, CPU throttling). Validate onboarding behavior and inventory cleanliness. 8. Summary & Best Practices Checklist for golden image: Script staged, not executed on master; executes only on child VMs at final boot stage. Shared Security Intelligence path configured; cache maintenance pre-run. FSLogix exclusions present prior to first user logon. RTP and cloud protection enabled; scans scheduled with randomization; CPU load factor tuned. Common pitfalls & fixes: Golden image onboarded → Offboard + clean registry/cache; reseal. Script runs before final hostname → Duplicate device records. Delay script until last reboot/final rename. No exclusions for FSLogix → Long logons/black screens. Add VHD/VHDX exclusions and share paths. Simultaneous scans across hosts → Enable randomization; schedule during off‑hours. References Onboard non‑persistent VDI devices: https://learn.microsoft.com/en-us/defender-endpoint/configure-endpoints-vdi Onboard Windows devices in Azure Virtual Desktop: https://learn.microsoft.com/en-us/defender-endpoint/onboard-windows-multi-session-device Configure Microsoft Defender Antivirus on RDS/VDI: https://learn.microsoft.com/en-us/defender-endpoint/deployment-vdi-microsoft-defender-antivirus FSLogix prerequisites (AV exclusions): https://learn.microsoft.com/en-us/fslogix/overview-prerequisites Configure AV exclusions (file/extension/folder): https://learn.microsoft.com/en-us/defender-endpoint/configure-extension-file-exclusions-microsoft-defender-antivirus Create and manage device tags: https://learn.microsoft.com/en-us/defender-endpoint/machine-tags Advanced features (hide duplicate records): https://learn.microsoft.com/en-us/defender-endpoint/advanced-features Schedule antivirus scans using Group Policy: https://learn.microsoft.com/en-us/defender-endpoint/schedule-antivirus-scans-group-policy Troubleshoot MDAV scan issues (CPU throttling, idle scans): https://learn.microsoft.com/en-us/defender-endpoint/troubleshoot-mdav-scan-issuesMicrosoft Defender for Endpoint (MDE) Live Response and Performance Script.
Importance of MDE Live Response and Scripts Live Response is crucial for incident response and forensic investigations. It enables analysts to: Collect evidence remotely. Run diagnostics without interrupting users. Remediate threats in real time. For more information on MDE Live Response visit the below documentation. Investigate entities on devices using live response in Microsoft Defender for Endpoint - Microsoft Defender for Endpoint | Microsoft Learn PowerShell scripts enhance this capability by automating tasks such as: Performance monitoring. Log collection. Configuration validation. This automation improves efficiency, consistency, and accuracy in security operations. For more details on running performance analyzer visit the below link. Performance analyzer for Microsoft Defender Antivirus - Microsoft Defender for Endpoint | Microsoft Learn While performance analyzer is run locally on the system to collect Microsoft Defender Anti-Virus performance details , in this document we are describing on running the performance analyzer from MDE Live Response console. This is a situation where Security administrators do not have access to the servers managed by Infra administrators. Prerequisites Required Roles and Permissions To use Live Response in Microsoft Defender for Endpoint (MDE), specific roles and permissions are necessary. The Security Administrator role, or an equivalent custom role, is typically required to enable Live Response within the portal. Users must possess the “Manage Portal Settings” permission to activate Live Response features. Permissions Needed for Live Response Actions Active Remediation Actions under Security Operations: Take response actions Approve or dismiss pending remediation actions Manage allowed/blocked lists for automation and indicators Unified Role-Based Access Control (URBAC): From 16/02/2025, new customers must use URBAC. Roles are assigned to Microsoft Entra groups. Access must be assigned to device groups for Live Response to function properly. Setup Requirements Enable Live Response: Navigate to Advanced Features in the Defender portal. Only users with the “Manage Portal Settings” permission can enable this feature. Supported Operating System Versions: Windows 10/11 (Version 1909 or later) Windows Server (2012 R2 with KB5005292, 2016 with KB5005292, 2019, 2022, 2025) macOS and Linux (specific minimum versions apply) Actual Script Details and Usage The following PowerShell script records Microsoft Defender performance for 60 seconds and saves the output to a temporary file: # Get the default temp folder for the current user $tempPath = [System.IO.Path]::GetTempPath() $outputFile = Join-Path -Path $tempPath -ChildPath "DefenderTrace.etl" $durationSeconds = 60 try { Write-Host "Starting Microsoft Defender performance recording for $durationSeconds seconds..." Write-Host "Recording will be saved to: $outputFile" # Start performance recording with duration New-MpPerformanceRecording -RecordTo $outputFile -Seconds $durationSeconds Write-Host "Recording completed. Output saved to $outputFile" } catch { Write-Host "Failed to start or complete performance recording: $_" } 🔧 Usage Notes: Run this script in an elevated PowerShell session. Ensure Defender is active, and the system supports performance recording. The output .etl file can be analyzed using performance tools like Windows Performance Analyzer. Steps to Initiate Live Response Session and Run the script. Below are the steps to initiate a Live Response session from Security.Microsoft.com portal. Below screenshot shows that console session is established. Then upload the script file to console library from your local system. Type “Library” to list the files. You can see that script got uploaded to Library. Now you execute the script by “run <file name>” command. Output of the script gets saved in the Library. Run “getfile <path of the file>” to get the file downloaded to your local system download folder. Then you can run Get-MpPerformanceReport command from your local system PowerShell as shown below to generate the report from the output file collected in above steps. Summary and Benefits This document outlines the use of MDE Live Response and PowerShell scripting for performance diagnostics. The provided script helps security teams monitor Defender performance efficiently. Similar scripts can be executed from Live Response console including signature updates , start/stop services etc. These scripts are required as a part of security investigation or MDE performance troubleshooting process. Benefits: Faster incident response through remote diagnostics. Improved visibility into endpoint behaviour. Automation of routine performance checks. Enhanced forensic capabilities with minimal user disruption.
Allow list to bypass attachments quarantine by Malware Agent
We have Exchange 2013 CU23 on-premises. We use Knowbe4 to send phishing test to employees. Some phishing emails have Word, Excel or Powerpoint attachments. The malware gents quarantines the attachment and replaces the attachment with a text file. I have installed the Connection Filtering Agent and added Knowbe4's phishing email server ip addresses using Add-IPAllowListEntry. The only way to get the email attachment is to set the malware filter to bypass filtering to true. Knowbe4 uses a sender's email address that is not knowbe4.com. I added a sample email address to BypassSenderDomains and email attachment was quarantined. Does Exchange 2013 on-premises have the ability to bypass the email attachment scan using a whitelist? Thanks for all replies. Jason M.
