Guy's Scripting Ezine - 95 WMI Script to Check your Security Log

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Contents for Ezine 95 - WMI Script to Check your Security Log

• This Week's Secret
• What can WMI do for you?
• WMI Methods and Mission
• Learning Points
• Summary of WMI

This Week's Secret

My research reminds me the secret of WMI is that the operating system knows everything; it must be all seeing to perform its job.  Fortunately, Microsoft allow us to share this privileged information thanks to WMI commands.

This Week's Mission

This week's advanced script interrogates the event logs and outputs the results to a text file.  For instance, we may want to discover how many illegal attempts have been made to logon as administrator.  Our mission emphasises the ability of scripts to automate boring and time-consuming tasks, such as scouring the logs for one particular Event ID.  This script also illustrates my mantra of how a manual walk through of the task, helps us understand the commands and thus build a better script.

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Real work v Getting started

In the real world, we would concentrate on detecting illegal attempts to logon as administrator.  As this is unlikely to have happened on your test system, therefore, purely to get some action in the output file, I substituted Event ID 680 success for 675 failure.

Walk-through

A walk through is important not only for understanding my script, but also to amend the Event IDs for your scenario.  Frankly, if you take my advice then you will gain control of this script; whereas if you don't have a walk through of the Event Viewer, I fear that all which follows, will seem as clear as mud.

1. Open Event Viewer
2. Match what you see in the security log with variables, strLogType, intNumberID and intEventType in my script.
3. Select Security Log (Not System)  WMI variable strLogType = "'Security'" Note one set of single quotes, inside one set of double quotes, no spaces.
4. Event ID number intNumberID value = 680.  Feel free to research our own numbers
5. Filter for Event 680  (Substitute 675 for illegal logon)
6. Filter for Success intEventType = 4 (Substitute intEventType = 5 for failures)

WMI Script to Check the Event Log

Normally I prefer to build WMI scripts in stages but on this occasion, I created only the final script.  I am assuming that you have a grounding in VBScript in general and FSO in particular.

When we ask WMI to interrogate the Event Logs, the key Win32 object is called, Win32_NTLogEvent.  Take care with the spelling as there other objects beginning with Win32_NTLog....

As ever, my script will get you started, but it is worth understanding where you could change the values to suit your Windows network.

Instructions for Creating your VBScript to Check Administrator Logons

1. Pre-requisites.  For this script to work, you need access to a Windows computer with a Security Log.
2. To reduce the chance of an authentication problem, I would first run this script at a Domain Controller.  If that is not possible, run the script from a member server on an XP machine and edit strComputer on line 15.
3. Check the strFolder and strFile values.  Where do you wish the script to appear?
4. Copy and paste into notepad, or a good script editor. 
5. Press OK when confronted by a message box, which says "Press OK and Wait 30 seconds (ish)"
6. Just open your text file from the folder displayed by Explorer!

VBScript Tutorial - Learning Points

1) Begin by checking the variables.  Experiment not only with strComputer, but also with intNumberID.  Double check Win32_ object name.

2) Here is a tiny addition to join two output properties and then write them on the same line.   strFile.WriteLine("Category: " & objItem.Category _
& " string " & objItem.CategoryString) A tiny improvement to save space in the output file.

3) Another cosmetic VBScript effect is to name the file after the Event Log ID,
strFileName = "\Event" & intNumberID & ".txt".  Although such improvements are minor, each contributes to a more professional script.

4) Although the VBScript example was getting rather long, I still could not resist adding a command to open the folder when the script creates the output file.
Set objShell = CreateObject("WScript.Shell")
objShell.run ("Explorer" &" " & strPath & "\" ).

5) I admit that I have ignored the FSO (File System Object) section, which writes the information to the file.  However, I do cover this important feature of VBScript in other ezines and pages on my website.

Summary of WMI

Remember that the operating system knows everything.  Thank Microsoft for providing a library of WMI commands with which to interrogate systems like the Event Logs.  WMI scripting is tricky because there are so many elements.  Take the time to have a walk through of how you examine an Event Log property sheet.  In particular, match the Event ID, Success or Failure and type of Log with variables in my script.

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