Disable new DMA devices when this computer is locked
Verified with Windows 11 25H2 — updated on July 10, 2026
Supported on: At least Windows Server 2016, Windows 10 Version 1703
Path in the GPO console
Computer Configuration\Administrative Templates\Windows Components\BitLocker Drive Encryption Description
This policy setting allows you to block direct memory access (DMA) for all Thunderbolt hot pluggable PCI downstream ports until a user logs into Windows. Once a user logs in, Windows will enumerate the PCI devices connected to the host Thunderbolt PCI ports. Every time the user locks the machine, DMA will be blocked on hot plug Thunderbolt PCI ports with no children devices, until the user logs in again. Devices which were already enumerated when the machine was unlocked will continue to function until unplugged or the system is rebooted or hibernated. This policy setting is only enforced when BitLocker or device encryption is enabled. Note: Some PCs may not be compatible with this policy if the system firmware enables DMA for newly attached Thunderbolt devices before exposing the new devices to Windows.
Registry
Software\Policies\Microsoft\FVE Value name: DisableExternalDMAUnderLock
Enabled: DisableExternalDMAUnderLock = 1
Disabled: DisableExternalDMAUnderLock = 0
Export Builder
BETAConfigure the state, scope and options, then generate .reg, PowerShell, Intune and SCCM outputs — or add the setting to a multi-setting collection.
These exports write the registry — this is not a managed GPO. ⓘ
.reg file
Windows Registry Editor Version 5.00
; Exported from gporais.com
; Policy: Disable new DMA devices when this computer is locked
; State: Enabled
; Supported on: At least Windows Server 2016, Windows 10 Version 1703
[HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\FVE]
"DisableExternalDMAUnderLock"=dword:00000001More formats (PowerShell, Intune, SCCM)
PowerShell
# Exported from gporais.com
# Policy: Disable new DMA devices when this computer is locked
# State: Enabled
# Supported on: At least Windows Server 2016, Windows 10 Version 1703
$path = 'HKLM:\Software\Policies\Microsoft\FVE'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'DisableExternalDMAUnderLock' -Value 1 -Type DWordIntune XML
No direct Policy CSP / OMA-URI mapping for this policy. Use the Intune Remediation tab, or ingest the ADMX in Intune.Intune Remediation
# === Detection script ===
# Exported from gporais.com
# Policy: Disable new DMA devices when this computer is locked
# State: Enabled
# Supported on: At least Windows Server 2016, Windows 10 Version 1703
function Test-RegistryValue {
param(
[Parameter(Mandatory = $true)][string]$Path,
[Parameter(Mandatory = $true)][string]$Name,
[object]$Expected,
[ValidateSet('String', 'DWord', 'MultiString')][string]$Kind = 'String',
[switch]$Absent
)
try {
$item = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction Stop
} catch {
return $Absent.IsPresent
}
if ($Absent.IsPresent) { return $false }
$actual = $item.$Name
if ($Kind -eq 'DWord') { return ([int64]$actual) -eq ([int64]$Expected) }
if ($Kind -eq 'MultiString') {
$actualValues = @($actual)
$expectedValues = @($Expected)
if ($actualValues.Count -ne $expectedValues.Count) { return $false }
for ($i = 0; $i -lt $expectedValues.Count; $i++) {
if ([string]$actualValues[$i] -ne [string]$expectedValues[$i]) { return $false }
}
return $true
}
return [string]$actual -eq [string]$Expected
}
$checks = @(
(Test-RegistryValue -Path 'HKLM:\Software\Policies\Microsoft\FVE' -Name 'DisableExternalDMAUnderLock' -Expected 1 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Disable new DMA devices when this computer is locked
# State: Enabled
# Supported on: At least Windows Server 2016, Windows 10 Version 1703
$path = 'HKLM:\Software\Policies\Microsoft\FVE'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'DisableExternalDMAUnderLock' -Value 1 -Type DWordSCCM scripts
# Exported from gporais.com
# Policy: Disable new DMA devices when this computer is locked
# State: Enabled
# Supported on: At least Windows Server 2016, Windows 10 Version 1703
# SCCM Configuration Item guidance:
# Create a Configuration Item of type "Setting: Script".
# Discovery script: use the Detection script below.
# Remediation script: use the Remediation script below.
# Compliance rule: the Discovery script output equals 'Compliant'.
# === Detection script ===
# Exported from gporais.com
# Policy: Disable new DMA devices when this computer is locked
# State: Enabled
# Supported on: At least Windows Server 2016, Windows 10 Version 1703
function Test-RegistryValue {
param(
[Parameter(Mandatory = $true)][string]$Path,
[Parameter(Mandatory = $true)][string]$Name,
[object]$Expected,
[ValidateSet('String', 'DWord', 'MultiString')][string]$Kind = 'String',
[switch]$Absent
)
try {
$item = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction Stop
} catch {
return $Absent.IsPresent
}
if ($Absent.IsPresent) { return $false }
$actual = $item.$Name
if ($Kind -eq 'DWord') { return ([int64]$actual) -eq ([int64]$Expected) }
if ($Kind -eq 'MultiString') {
$actualValues = @($actual)
$expectedValues = @($Expected)
if ($actualValues.Count -ne $expectedValues.Count) { return $false }
for ($i = 0; $i -lt $expectedValues.Count; $i++) {
if ([string]$actualValues[$i] -ne [string]$expectedValues[$i]) { return $false }
}
return $true
}
return [string]$actual -eq [string]$Expected
}
$checks = @(
(Test-RegistryValue -Path 'HKLM:\Software\Policies\Microsoft\FVE' -Name 'DisableExternalDMAUnderLock' -Expected 1 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Disable new DMA devices when this computer is locked
# State: Enabled
# Supported on: At least Windows Server 2016, Windows 10 Version 1703
$path = 'HKLM:\Software\Policies\Microsoft\FVE'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'DisableExternalDMAUnderLock' -Value 1 -Type DWordBuilding a multi-setting collection? Add this setting and generate combined .reg / PowerShell / GPO scripts.