In a previous post we shared a PowerShell script that would allow an auditor to parse a list of groups and group members on a Microsoft Windows system as a part of a security assessment or baselining process. The question has come up though – what if someone wants to follow the same process but parse a list of Active Directory groups and their members instead?

It turns out that it is much easier to perform the task against Active Directory than it is to do it against a local Microsoft Windows local Security Accounts Manager (SAM) database. It seems that the native capabilities of the Active Directory PowerShell cmdlets is going to make it easier for us to accomplish this task.

The output requirement for this script will be the same as for the previous. The output should be in a CSV format that could be easily parsed by a spreadsheet program like Microsoft Excel. Also, like the previous script, empty groups should still be listed, but just without any group members listed along with them.

The code we used to parse a list of AD groups and their members is:

Get-ADGroup -Filter * | ForEach-Object { 
    $GroupName = $_.Name 
    $Members = Get-ADGroupMember $_.samaccountname -Recursive | foreach{$_.Name} 
        If ($Members.count -ge 1){
            $Out = $GroupName + "," + [String]::Join(",", $Members)
            $out | Out-File -append ad_group_members.txt
        }
        Else{
            $Out = $GroupName
            $out | Out-File -append ad_group_members.txt  
        }
    } 

Ideally an auditor would combine this script with our previous example and using PowerShell remoting run one script that would parse local and Active Directory groups at the same time and output the data as an easily readable file. But between the two examples, hopefully it will give you enough inspiration to make this usable for you in your audit efforts.

One step that has become a staple part of any audit of Microsoft Windows systems is a listing of all the local groups on the system. Listing all the groups on a system with all the members of that group can help establish a baseline for the security configuration of a system. Certainly groups like the local Administrators group is a concern during a security audit. Ideally though auditors would have the ability to look at the members of each group on a system and validate that the list of members is appropriate for that system.

As with many of the scripts we have recommended, we decided to write a script using PowerShell to pull the information from a local system. We also wanted to make sure that when we pulled the information from a system that we could parse it easily once we were done. Therefore we wrote the script to allow us to pull all the local computer groups from a system, with the members of the group, and then save it as a CSV file for easier parsing with Excel.

Here is the code we used for the script:

$GroupList = Get-WmiObject Win32_Group | ForEach {$_.name}

$ComputerName = "."

ForEach ($GL in $GroupList)

{

    $Computer = [ADSI]("WinNT://" + $ComputerName + ",computer")

    $Group = $Computer.psbase.children.find($GL)

    $Members= $Group.psbase.invoke("Members") | %{$_.GetType().InvokeMember("Name", 'GetProperty', $null, $_, $null)}

        If ($Members.count -ge 1){
            $Out = $GL + "," + [String]::Join(",", $Members)
            $out | Out-File -append local_group_members.csv
        }
        Else{
            $Out = $GL
            $out | Out-File -append local_group_members.csv
        }

}

We ran into a couple issues when writing the script. One was the formatting of the output to a CSV file. Normally we would use an EXPORT-CSV cmdlet to do that, but in this case since we had multiple data sources we had to do some custom formatting. Also since some of the groups were empty, we had to add the IF clause to make sure that even blank groups were reported in our output.

Once the concept of the script starts to make sense to you, it should be an easy next step to consider adding PowerShell remoting capabilities or a computer name list to the script to parse multiple systems at once. You might also consider saving the output from the script in a format (such as HTML) that is easier to read and include in your audit reports.

We hope the script is useful as you audit Microsoft Windows servers or establish security baselines for those systems.