Tim D'Annecy

#Powershell #Windows

Recently, I was trying to run a Powershell command to retrieve the list of Local Admin accounts on a domain-joined machine.

I ran this command in Powershell 5.1 and 7.2.5:

Get-LocalGroupMember -Group Administrators

I received an error that something was wrong with the command.

Get-LocalGroupMember : Failed to compare two elements in the array. At line:1 char:1

A SuperUser post [A] suggested that the error is caused by invalid admin accounts that are not cleaned up during domain join or AAD join. The post suggests running the following Powershell command to remove the invalid admin accounts:

# Clean-AdministratorGroup.ps1
# https://gist.github.com/tdannecy/daf057ab9b9280290efb34677d9c0ea8
# https://superuser.com/a/1481036

function Clean-AdministratorGroup {
    $administrators = @(
        ([ADSI]"WinNT://./Administrators").psbase.Invoke('Members') |
        ForEach-Object { 
            $_.GetType().InvokeMember('AdsPath', 'GetProperty', $null, $($_), $null) 
        }
    ) -match '^WinNT';
        
    $administrators = $administrators -replace 'WinNT://', ''
        
    $administrators | ForEach-Object {   
        if ($_ -like "$env:COMPUTERNAME/*" -or $_ -like "AzureAd/*") {
            continue;
        }
        Remove-LocalGroupMember -group 'Administrators' -member $_
    }
}
Clean-AdministratorGroup

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