Do not allow COM port redirection
Verified with Windows 11 25H2 — updated on July 30, 2026
Supported on: At least Windows Server 2003 operating systems or Windows XP Professional
Path in the GPO console
Computer Configuration\Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Device and Resource Redirection Description
This policy setting specifies whether to prevent the redirection of data to client COM ports from the remote computer in a Remote Desktop Services session. You can use this setting to prevent users from redirecting data to COM port peripherals or mapping local COM ports while they are logged on to a Remote Desktop Services session. By default, Remote Desktop Services allows this COM port redirection. If you enable this policy setting, users cannot redirect server data to the local COM port. If you disable this policy setting, Remote Desktop Services always allows COM port redirection. If you do not configure this policy setting, COM port redirection is not specified at the Group Policy level.
Registry
SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services Value name: fDisableCcm
Enabled: fDisableCcm = 1
Disabled: fDisableCcm = 0
MDM / Intune (CSP)
./Device/Vendor/MSFT/Policy/Config/ADMX_TerminalServer/TS_CLIENT_COM 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: Do not allow COM port redirection
; State: Enabled
; Supported on: At least Windows Server 2003 operating systems or Windows XP Professional
[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services]
"fDisableCcm"=dword:00000001More formats (PowerShell, Intune, SCCM)
PowerShell
# Exported from gporais.com
# Policy: Do not allow COM port redirection
# State: Enabled
# Supported on: At least Windows Server 2003 operating systems or Windows XP Professional
$path = 'HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'fDisableCcm' -Value 1 -Type DWordIntune XML
OMA-URI: ./Device/Vendor/MSFT/Policy/Config/ADMX_TerminalServer/TS_CLIENT_COM
Data type: String
Value:
<enabled/>Intune Remediation
# === Detection script ===
# Exported from gporais.com
# Policy: Do not allow COM port redirection
# State: Enabled
# Supported on: At least Windows Server 2003 operating systems or Windows XP Professional
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
}
$checks = @(
(Test-RegistryValue -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services' -Name 'fDisableCcm' -Expected 1 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Do not allow COM port redirection
# State: Enabled
# Supported on: At least Windows Server 2003 operating systems or Windows XP Professional
$path = 'HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'fDisableCcm' -Value 1 -Type DWordSCCM scripts
# Exported from gporais.com
# Policy: Do not allow COM port redirection
# State: Enabled
# Supported on: At least Windows Server 2003 operating systems or Windows XP Professional
# 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: Do not allow COM port redirection
# State: Enabled
# Supported on: At least Windows Server 2003 operating systems or Windows XP Professional
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
}
$checks = @(
(Test-RegistryValue -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services' -Name 'fDisableCcm' -Expected 1 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Do not allow COM port redirection
# State: Enabled
# Supported on: At least Windows Server 2003 operating systems or Windows XP Professional
$path = 'HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'fDisableCcm' -Value 1 -Type DWordBuilding a multi-setting collection? Add this setting and generate combined .reg / PowerShell / GPO scripts.