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Zacon 2 - PowerShell Basics Part 2


The much delayed part 2 is finally here and the topic of the day is poking the system. This is much like poking a bear but hopefully less painfull. The purpose of poking the system is to go about showing how to interact with with the underlying OS of choice.

Getting Started :


First of you need to have some basic powershell skills , my original post can be found here. Its pretty simple and follows on the video so you dont have to read to much if you dont want to.

Grab the script for this post from here. Unlike the previous post I wont be explaining line by line , rather function by function.

Get-Users :


This is a rather simple but interesting example of working with WMI , it points out 2 things.

  1. That you can get interesting system data via WMI

    • We are able to get all the users in the system via WMI and while I am not familiar with using the normal windows shell to get this info , it can not be easier than this.

    • The other fact that is not obvious is that you can use this on a remote system to get simliar results without much changes to the code

  2. Also how you would get started using WMI

    • It shows the basic syntax for making a WMI call, if it was not apprent you simply call gwmi with the name of the class you want data from. In this case the class is win32_useraccount. To get a list of classes that you can use gwmi -list.

Get-Applications :


This is a bit of a simpler example which just returns a list of applications installed on the users machine. It can be expanded alot more to do things such as simpler searching or even calling the untinstall method on a application of choice.

Get-FirewallRules:


This takes what we have learnt up until now a little further. First of all it takes in a parameter of the users choice, but it also provides a default option so that if the user does not provide one the function will not crash.

Also this functions shows you how to work with com objects in powershell. The reason we do this is because there is no simple public WMI interface and the com interface is alot simpler to work with. The function also shows how you do inline filtering by using the powershell where command ( either ? or where will work )

Get-ADComputers :


This uses a little more complex functionality , but its nothing that would not have been covered in the previous functions. The 2 major differences between the previous functions is :

  1. That the function casts the string “objectcategory=computer” to a Active Directory Searcher object. The searcher is a little bit complex for this post so I wont go into detail about how it works. For now just know that it allows you to performa AD searches via the commmandline and more specifically powershell.

  2. How to loop over each object that the search returns, if you are a coder with previous experiance then the loop is the equivalent to a foreach loop. If it hasnt become apprent already this is the loop %{([adsi]$_.path).cn + $_.properties.operatingsystemversion} . You can use either % or ForEach-Object , what ever is between the {} is executed on each step. If you need access to the object that is being access you need to use the $_ variable.

Get-LocalOsVersion :


This method does nothing new really except that it specifies which columns need to be returned since the default data can be a bit much. Use this when a object has properties that you need access to.

While I hope that covers the script a bit more in depth than what I managed to talk about in the video. If there is anything that has not been covered in enough detail or has been covered incorrectly please let me know so what I can correct it.

If you find any issues please catch me in #zacon on atrum or on twitter(@RC1140).