Custom Classes: Deny write access
Verified with Windows 11 25H2 — updated on July 30, 2026
Supported on: At least Windows Vista
Path in the GPO console
Computer Configuration\Administrative Templates\System\Removable Storage Access Description
This policy setting denies write access to custom removable storage classes. If you enable this policy setting, write access is denied to these removable storage classes. If you disable or do not configure this policy setting, write access is allowed to these removable storage classes.
Registry
HKLM
Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write Value name: Deny_Write
Enabled: Deny_Write = 1
Disabled: Deny_Write = 0
MDM / Intune (CSP)
./Device/Vendor/MSFT/Policy/Config/ADMX_RemovableStorage/CustomClasses_DenyWrite_Access_2 Microsoft Learn documentation Mapping data: Microsoft Learn (CC BY 4.0)
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: Custom Classes: Deny write access
; State: Enabled
; Supported on: At least Windows Vista
[HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write]
"Deny_Write"=dword:00000001
[HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write\List]
; List values: enter one value per line in the builder UI.More formats (PowerShell, Intune, SCCM)
PowerShell
# Exported from gporais.com
# Policy: Custom Classes: Deny write access
# State: Enabled
# Supported on: At least Windows Vista
$path = 'HKLM:\Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'Deny_Write' -Value 1 -Type DWord
$path = 'HKLM:\Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write\List'
New-Item -Path $path -Force | Out-Null
# List values: enter one value per line in the builder UI.Intune XML
OMA-URI: ./Device/Vendor/MSFT/Policy/Config/ADMX_RemovableStorage/CustomClasses_DenyWrite_Access_2
Data type: String
Value:
<enabled/>
<!-- CustomClasses_List: enter one value per line before copying this XML payload. -->Intune Remediation
# === Detection script ===
# Exported from gporais.com
# Policy: Custom Classes: Deny write access
# State: Enabled
# Supported on: At least Windows Vista
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
}
# HKLM:\Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write\List: List values: enter one value per line in the builder UI.
$checks = @(
(Test-RegistryValue -Path 'HKLM:\Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write' -Name 'Deny_Write' -Expected 1 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Custom Classes: Deny write access
# State: Enabled
# Supported on: At least Windows Vista
$path = 'HKLM:\Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'Deny_Write' -Value 1 -Type DWord
$path = 'HKLM:\Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write\List'
New-Item -Path $path -Force | Out-Null
# List values: enter one value per line in the builder UI.SCCM scripts
# Exported from gporais.com
# Policy: Custom Classes: Deny write access
# State: Enabled
# Supported on: At least Windows Vista
# 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: Custom Classes: Deny write access
# State: Enabled
# Supported on: At least Windows Vista
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
}
# HKLM:\Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write\List: List values: enter one value per line in the builder UI.
$checks = @(
(Test-RegistryValue -Path 'HKLM:\Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write' -Name 'Deny_Write' -Expected 1 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Custom Classes: Deny write access
# State: Enabled
# Supported on: At least Windows Vista
$path = 'HKLM:\Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'Deny_Write' -Value 1 -Type DWord
$path = 'HKLM:\Software\Policies\Microsoft\Windows\RemovableStorageDevices\Custom\Deny_Write\List'
New-Item -Path $path -Force | Out-Null
# List values: enter one value per line in the builder UI.Building a multi-setting collection? Add this setting and generate combined .reg / PowerShell / GPO scripts.