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In Microsoft Intune, configure Enumeration policy for external devices incompatible with Kernel DMA Protection under DMA Guard. Choose Block all (value 0) for the strongest restriction, Only after log in/screen unlock (value 1) for a compatibility-conscious deployment, or Allow all (value 2) when compatibility is explicitly prioritized. The policy affects external DMA-capable PCIe devices that are incompatible with DMA remapping; it is not a general USB-blocking rule.
What Device Enumeration Policy protects
Some externally connected PCIe peripherals can access system memory directly through direct memory access (DMA). Without appropriate remapping controls, an attacker with physical access could use a peripheral while Windows is locked or before sign-in to target data held in memory, such as credentials, encryption keys, or other secrets.
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Windows Kernel DMA Protection uses platform firmware, the IOMMU and DMA-remapping-compatible drivers to constrain that access. Intune’s policy controls whether an external DMA-capable device that is incompatible with DMA remapping is enumerated before authentication. It mitigates this attack path; it does not provide complete protection against every cold-boot technique or replace Secure Boot, BitLocker, endpoint protection, firmware security and physical controls. See Microsoft’s explanation of Kernel DMA Protection at Microsoft Learn.
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What it does not block
This is not a removable-storage or universal USB policy. Ordinary USB peripherals do not necessarily perform DMA themselves, and Microsoft distinguishes non-PCI devices from the external PCIe devices covered here. Thunderbolt and other hot-pluggable PCIe paths are common examples, but the deciding factor is DMA-remapping compatibility, not a generic “trusted” or “untrusted” label.
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The DmaGuard policy also excludes 1394/FireWire, PCMCIA and ExpressCard devices. Those interfaces require separate controls or a hardware-removal decision. A complete peripheral allowlist must be implemented with appropriate device-control tools rather than inferred from this one setting.
Choose the policy value
| Value | Intune label | Behavior | When to use |
|---|---|---|---|
0 |
Block all | Blocks all affected incompatible external devices at all times, including before sign-in and while locked. | Use for maximum pre-authentication protection after testing docks, adapters, storage, displays, networking and specialist PCIe equipment. |
1 |
Only after log in/screen unlock | Allows affected incompatible devices only after the user signs in or unlocks the screen. | Use as a balanced pilot value when users need selected peripherals after authentication. This is the CSP and Windows default. |
2 |
Allow all | Allows all external DMA-capable PCIe devices without this enumeration restriction. | Use only for a documented compatibility exception, risk acceptance or temporary troubleshooting. It provides the least protection. |
Microsoft’s Windows MDM security baseline lists Block all as its baseline default, but that baseline choice does not remove the need to test the actual hardware fleet. Check whether a baseline already configures the setting before creating another profile.
Prerequisites and scope
- A Windows device enrolled in Intune and assigned to the policy.
- Windows 10 version 1809 or later, on a supported Pro, Enterprise, Education or IoT Enterprise edition, as documented by the DmaGuard Policy CSP.
- Hardware and system firmware that support Kernel DMA Protection, with the feature enabled in BIOS/UEFI. Intune cannot add this capability to unsupported hardware.
- A pilot device group, a reboot window and an inventory of business-critical Thunderbolt, docking, storage, display and specialist peripherals.
- A recovery path, such as an unassigned test device or break-glass administrator process.
On each pilot computer, run msinfo32.exe, open System Summary and verify the Kernel DMA Protection field. Record whether it is supported and enabled before interpreting policy results.
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Configure it with the Intune Settings Catalog
- Sign in to the Microsoft Intune admin center.
- Open Devices, then Configuration, and select Create (or + Create) and New policy.
- Set Platform to Windows 10 and later and Profile type to Settings catalog.
- Enter a descriptive name and, if useful, document the selected value, pilot scope and rollback owner.
- Select Add settings, browse to DMA Guard, and select Device Enumeration Policy.
- Choose Block all, Only after log in/screen unlock or Allow all.
- Continue through scope tags, assignments and review. Assign the first deployment to a dedicated device pilot group, not the whole production fleet.
- Select Create. Sync the pilot from Company Portal or Windows Settings, then restart it. Microsoft documents a system restart as required for the policy to take effect.
Portal wording can change. Search for the exact setting name and confirm that the underlying CSP is DmaGuard/DeviceEnumerationPolicy rather than relying on a screenshot.
Deploy with a custom OMA-URI
If the Settings Catalog entry is unavailable or you need a custom profile, create a Windows custom configuration profile with these values:
| OMA-URI | ./Device/Vendor/MSFT/Policy/Config/DmaGuard/DeviceEnumerationPolicy |
|---|---|
| Data type | Integer |
| Value | 0 for Block all, 1 for Only after log in/screen unlock, or 2 for Allow all |
The setting is device-scoped. Microsoft’s Graph mapping names the corresponding Intune property DmaGuardDeviceEnumerationPolicy and uses the CSP offset /Config/DmaGuard/DeviceEnumerationPolicy; do not substitute a shortened path for the full OMA-URI. See the Windows CSP Graph mapping.
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Roll out in stages
- Create a dedicated pilot device group and assign value
1first unless your tested requirement already mandates value0. - Test while the device is at the lock screen and again after sign-in. Include docks, external displays, storage, networking and any specialized PCIe-connected equipment.
- Review assignment, applicability and per-device setting status in Intune, then restart devices after receipt.
- Collect support results and identify peripherals that require an exception or a DMA-remapping-compatible driver.
- Move tested groups to value
0when the security requirement justifies the compatibility impact. Keep exclusions narrowly scoped and documented.
Before deployment, inspect security baselines and other configuration profiles. Two profiles targeting the same CSP can create conflicts or unclear ownership; Intune conflict reporting should be resolved rather than masked by another assignment.
Verify deployment and enforcement
Check Intune reporting
Distinguish assignment from enforcement. A device can be assigned, check in successfully and report a setting as succeeded while still requiring a restart or while using hardware outside the policy scope. Review the policy’s device status, per-device configuration status, last check-in and any conflict or applicability error.
Check the Windows prerequisite
Run msinfo32.exe and confirm Kernel DMA Protection is supported and enabled. If it is unavailable, changing the Intune value cannot create the missing platform capability.
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Check client diagnostics
Open Event Viewer > Applications and Services Logs > Microsoft > Windows > DeviceManagement-Enterprise-Diagnostics-Provider > Admin. HTMD recommends looking for Event ID 813 as an indication of successful policy processing. Treat that event as a processing signal, not proof that every peripheral is blocked; combine it with Intune status, a restart and functional tests.
Test both authentication states
- At the Windows lock screen, connect an affected incompatible device and observe whether it enumerates.
- Sign in or unlock and repeat the test.
- For value
0, the affected device should remain restricted in both states. - For value
1, it may become available only after sign-in or unlock. - For value
2, this policy imposes no enumeration restriction.
A DMA-remapping-compatible device can remain available under a restrictive value; that result is expected.
Troubleshoot common failures
Kernel DMA Protection is unsupported or disabled
If msinfo32.exe reports unsupported or disabled, verify the OEM’s hardware support, apply a manufacturer-approved firmware update when available and check BIOS/UEFI settings. Replace unsupported hardware if the requirement is mandatory; Intune cannot retrofit Kernel DMA Protection.
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The setting is missing in Intune
Confirm enrollment, Windows platform and edition, profile type, assignment scope and whether another baseline or profile owns the setting. Use the CSP documentation as the authoritative fallback and deploy the custom OMA-URI if appropriate.
The policy reports success but the peripheral still works
- The device may support DMA remapping and therefore is allowed.
- It may not be an affected external PCIe device.
- The computer may not have restarted.
- Kernel DMA Protection may not be active.
- Value
1permits the device after sign-in. - The interface may be outside this policy’s scope, or another policy may override it.
A required dock or adapter stops working
- Determine whether failure occurs only while the screen is locked.
- Test after sign-in if the assigned value is
1. - Check the peripheral’s DMA-remapping-compatible driver support.
- Review Intune status and the MDM diagnostic log.
- Temporarily remove the device from the pilot assignment or change it to value
1. - Restart and confirm recovery, then document a narrow exception instead of changing the entire fleet to value
2.
Do not confuse this with the Direct Memory Access setting
Intune also exposes a separate Direct Memory Access restriction. Its CSP is DataProtection/AllowDirectMemoryAccess; it blocks DMA for hot-pluggable PCI downstream ports until a user signs in. DmaGuard/DeviceEnumerationPolicy, by contrast, controls enumeration of external DMA-capable devices that are incompatible with DMA remapping. These controls address related risks but are not interchangeable. Microsoft’s Windows device-restriction reference describes the separate setting at this page.
Group Policy and registry mapping
For hybrid environments, Microsoft maps the same control to:
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Computer Configuration > Administrative Templates > System > Kernel DMA Protection - Policy name: Enumeration policy for external devices incompatible with Kernel DMA Protection
- Registry:
HKLMSoftwarePoliciesMicrosoftWindowsKernel DMA Protection - Value:
DeviceEnumerationPolicyas aREG_DWORD - ADMX:
DmaGuard.admx
Use Intune or Group Policy for normal enterprise deployment. The registry mapping is primarily useful when diagnosing effective policy and ownership.
Rollback and operational ownership
- Remove the affected device from the pilot assignment or add a narrowly scoped exclusion.
- Change the assigned value to
1, or remove the assignment when a full rollback is required. - Allow the device to check in, then restart it.
- Confirm peripheral recovery and record the exception, hardware model, driver and reason.
- Re-test before expanding value
0to additional groups.
For a Windows fleet already managed with Microsoft endpoint tools, Intune is the most direct deployment path because the DmaGuard CSP is documented and available through Settings Catalog or custom MDM configuration. Any alternative UEM must be checked for arbitrary Windows CSP delivery, device targeting, conflict reporting, reboot tracking and hardware inventory before it is treated as equivalent.
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