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Remove-PowerShellV2.ps1
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Remove-PowerShellV2.ps1
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<#
.SYNOPSIS
This cmdlet is used to remove PowerShell version 2 from a device if it is installed. PowerShell v2 is able to be used in a PowerShell downgrade attack which bypasses modern PowerShell defenses.
.DESCRIPTION
This cmdlet checks whether or not PowerShell version 2 is installed and then removes it if it is.
.PARAMETER ComputerName
This parameter is used to define a single device or a list of devices to disable PowerShell version 2 on
.EXAMPLE
Remove-PowerShellV2
# This example removes PowerShell version 2 if it is installed on the local machine
.EXAMPLE
Remove-PowerShellV2 -ComputerName DC01,Desktop20
# This example removes PowerShell version 2 from the remote devices DC01 and Desktop20
.NOTES
Author: Robert H. Osborne
Alias: tobor
Contact: [email protected]
.INPUTS
None
.OUTPUTS
None
.LINK
https://osbornepro.com
https://writeups.osbornepro.com
https://github.com/tobor88
https://gitlab.com/tobor88
https://www.powershellgallery.com/profiles/tobor
https://www.linkedin.com/in/roberthosborne/
https://www.credly.com/users/roberthosborne/badges
https://www.hackthebox.eu/profile/52286
#>
Function Remove-PowerShellV2 {
[CmdletBinding()]
param(
[Parameter(
Mandatory=$False,
Position=0,
ValueFromPipeline=$True,
ValueFromPipelineByPropertyName=$True)] # End Parameter
[Alias('cn','Computer')]
[ValidateNotNullOrEmpty()]
[String[]]$ComputerName
) # End param
Switch ($PSBoundParameters.Keys) {
'ComputerName' {
ForEach ($C in $ComputerName)
{
$SessionOption = New-PSSessionOption -SkipCACheck -SkipCNCheck -SkipRevocationCheck
# This option to an attempt to accomdate any environment and should not be needed if WinRM over HTTPS is configured correctly
Invoke-Command -HideComputerName "$C.$env:USERDNSDOMAIN" -UseSSL -SessionOption $SessionOption -ScriptBlock {
Write-Verbose "[*] Checking whether or not PowerShell version 2 is installed on the $env:COMPUTERNAME"
$State = (Get-WindowsOptionalFeature -Online -FeatureName MicrosoftWindowsPowerShellV2).State
Switch ($State)
{
"Enabled" {
Write-Output "[!] $env:COMPUTERNAME is vulnerable to a PowerShell downgrade attack"
Write-Output "[*] Removing PowerShell Version 2 to remediate PowerShell Downgrade Attack vulnerability"
Try
{
Disable-WindowsOptionalFeature -Online -FeatureName MicrosoftWindowsPowerShellV2Root -Remove
} # End Try
Catch
{
Write-Output "[*] SAFE: PowerShell version 2 is not installed on $env:COMPUTERNAME"
} # End Catch
} # End Enabled Switch
"Disabled" {
Write-Output "[*] SAFE: PowerShell version 2 is not installed on $env:COMPUTERNAME"
} # End Disabled Switch
} # End Switch
} # End Invoke-Command
} # End ForEach
} # End ComputerName Switch
Default {
Write-Verbose "[*] Checking whether or not PowerShell version 2 is installed on the host"
$State = (Get-WindowsOptionalFeature -Online -FeatureName MicrosoftWindowsPowerShellV2).State
Switch ($State)
{
"Enabled" {
Write-Output "[!] $env:COMPUTERNAME is vulnerable to a PowerShell downgrade attack"
Write-Output "[*] Removing PowerShell Version 2 to remediate PowerShell Downgrade Attack vulnerability"
Try
{
Disable-WindowsOptionalFeature -Online -FeatureName MicrosoftWindowsPowerShellV2Root -Remove
} # End Try
Catch
{
Write-Output "[*] SAFE: PowerShell version 2 is not installed on $env:COMPUTERNAME"
} # End Catch
} # End Enabled Switch
"Disabled" {
Write-Output "[*] SAFE: PowerShell version 2 is not installed on $env:COMPUTERNAME"
} # End Disabled Switch
} # End Switch
} # End Default Switch
} # End Switch
} # End Function Remove-PowerShellV2
# SIG # Begin signature block
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# SIG # End signature block