Create a list of local administrators with PowerShell

1.       Create folder :    C:\Temp

2.       Save a text file with the name servers.txt and add server names

3.       Create a .PS1 file with the name “ Get-LocalGroupMembers.ps1 ”with below PowerShell code:

**********************************************************   

 [CmdletBinding()]

Param(

    [Parameter(    ValueFromPipeline=$true,

                ValueFromPipelineByPropertyName=$true

                )]

    [string[]]

    $ComputerName = $env:ComputerName,

    [Parameter()]

    [string]

    $LocalGroupName = "Administrators",

    [Parameter()]

    [string]

    $OutputDir = "c:\temp"

)

Begin {

    $OutputFile = Join-Path $OutputDir "LocalGroupMembers.csv"

    Write-Verbose "Script will write the output to $OutputFile folder"

    Add-Content -Path $OutPutFile -Value "ComputerName, LocalGroupName, Status, MemberType, MemberDomain, MemberName"

}

Process {

    ForEach($Computer in $ComputerName) {

        Write-host "Working on $Computer"

        If(!(Test-Connection -ComputerName $Computer -Count 1 -Quiet)) {

            Write-Verbose "$Computer is offline. Proceeding with next computer"

            Add-Content -Path $OutputFile -Value "$Computer,$LocalGroupName,Offline"

            Continue

        } else {

            Write-Verbose "Working on $computer"

            try {

                $group = [ADSI]"WinNT://$Computer/$LocalGroupName"

                $members = @($group.Invoke("Members"))

                Write-Verbose "Successfully queries the members of $computer"

                if(!$members) {

                    Add-Content -Path $OutputFile -Value "$Computer,$LocalGroupName,NoMembersFound"

                    Write-Verbose "No members found in the group"

                    continue

                }

            }       

            catch {

                Write-Verbose "Failed to query the members of $computer"

                Add-Content -Path $OutputFile -Value "$Computer,,FailedToQuery"

                Continue

            }

            foreach($member in $members) {

                try {

                    $MemberName = $member.GetType().Invokemember("Name","GetProperty",$null,$member,$null)

                    $MemberType = $member.GetType().Invokemember("Class","GetProperty",$null,$member,$null)

                    $MemberPath = $member.GetType().Invokemember("ADSPath","GetProperty",$null,$member,$null)

                    $MemberDomain = $null

                    if($MemberPath -match "^Winnt\:\/\/(?\S+)\/(?\S+)\/") {

                        if($MemberType -eq "User") {

                            $MemberType = "LocalUser"

                        } elseif($MemberType -eq "Group"){

                            $MemberType = "LocalGroup"

                        }

                        $MemberDomain = $matches["CompName"]

                    } elseif($MemberPath -match "^WinNT\:\/\/(?\S+)/") {

                        if($MemberType -eq "User") {

                            $MemberType = "DomainUser"

                        } elseif($MemberType -eq "Group"){

                            $MemberType = "DomainGroup"

                        }

                        $MemberDomain = $matches["domainname"]

                    } else {

                        $MemberType = "Unknown"

                        $MemberDomain = "Unknown"

                    }

                Add-Content -Path $OutPutFile -Value "$Computer, $LocalGroupName, SUCCESS, $MemberType, $MemberDomain, $MemberName"

                } catch {

                    Write-Verbose "failed to query details of a member. Details $_"

                    Add-Content -Path $OutputFile -Value "$Computer,,FailedQueryMember"

                }

            }

        }

    }

}

End {}

***********************************************************

4.       Open PowerShell and point to Get-LocalGroupMembers.ps1 and use below commands to get the results.

.\Get-LocalGroupMembers.PS1 -ComputerName (Get-Content C:\temp\servers.txt)

Results will be saved as CSV file and at C:\Temp with the name “LocalGroupMembers.csv”

Source:  https://4sysops.com/archives/create-a-list-of-local-administrators-with-powershell/