Working with (custom) detection rules for Win32 apps

After my post of last week about Working with (custom) requirements for Win32 apps only one configuration subject of Win32 apps is left that I’ve discussed in detail, the detection rules for Win32. The format of this week is similar to that post and to previous posts about the different configuration subjects of Win32 apps. Detection rules must be used to determine the presence of a Win32 app. A Win32 app can have multiple detection rules. In that case every detection rule must be met to detect the app. That will help with making sure that the app installation will only be started when the app is not yet installed. In this post I’ll start with going through the different detection rule formats and I’ll end this post by looking at the administrator experience on a Windows device.

Detection rule

Now let’s start by having a look at the available detection rules of a Win32 app in Microsoft Intune. Let’s do that by first navigating to the location in the Microsoft Endpoint Manager admin center portal that provides the different detection rule format options for Win32 apps.

  1. Open the Microsoft Endpoint Manager admin center portal and navigate to Apps Windows > Windows apps to open the Windows – Windows apps blade
  2. On the Windows – Windows apps blade, select a Win32 app (or create a new one) and click Properties > Detection rules to open the Detection rules blade

On the Detection rules blade, the different detection rule formats of Win32 apps are shown. Those detection rule formats are categorized as mentioned below.

  1. Manually configure detection rules: This detection rule format enables the administrator to use a MSI product code, file or folder information or registry information for detecting the app.
  2. Use custom detection rules: This detection rule format enables the administrator to use a custom script for detecting the app.

The first category contains manual configurable detection rules. The manual configurable detection rules contains three different rule types that can be used to indicate the presence op the app. The first rule type in that list is MSI. That rule type enables the administrator to create a detection rule that must detect a specific MSI, or even a specific MSI version. This detection rule type can only be used once. A detection rule of this type requires the following configuration properties.

  • MSI product code – This property enables the administrator to configure the specific MSI product code that should be used to detect the installation of the app. When the installation contains an MSI, and this rule type is used, this property will be automatically populated.
  • MSI product version check – This property enables the administrator to configure also a specific version of the MSI product code that should be used to detect the installation of the app.

The second rule type in that list is File. That rule type enables the administrator to create a detection rule that must detect a specific file or folder, date, version, or size to determine the installation of the Win32 app. A detection rule of this type requires the configuration properties as mentioned below. This rule type is with its configuration properties nearly equal to the File rule type within requirement rules.

  • Path – This property enables the administrator to configure the full path of the folder that contains the file or folder that should be used to detect the installation of the app.
  • File or folder – This property enables the administrator to configure the file or folder that should be used to detect the installation of the app.
  • Detection method – This property enables the administrator to configure the method that should be used to detect the installation of the app. The following self explaining options are available.
    • File or folder exists
    • Date modified
    • Date created
    • String (version)
    • Size in MB
  • Associated with a 32-bit app on 64-bit clients – This property enables the administrator to configure that path environment variables are in 32-bit (yes) or 64-bit (no) context on 64-bit clients.

The third rule type in that list is Registry. That rule type enables the administrator to create a detection rule that must detect a specific registry setting based on value, string, integer, or version to determine the installation of the Win32 app. A detection rule of this type requires the configuration properties as mentioned below. This rule type is with its configuration properties nearly equal to the Registry rule type within requirement rules.

  • Key path – This property enables the administrator to configure the full path of the registry entry containing the value that should be used to detect the installation of the app.
  • Value name – This property enables the administrator to configure the name of the registry value that should be used to detect the installation of the app. When this property is empty, the detection will happen on the default value. The default value will also be used as detection value if the detection method is other than file or folder existence.
  • Detection method – This property enables the administrator to configure the method that should be used to detect the installation of the app. The following self explaining options are available.
    • Key exists
    • Key does not exist
    • String comparison
    • Version comparison
    • integer comparison
  • Associated with a 32-bit app on 64-bit clients – This property enables the administrator to configure that the search is in the 32-bit registry (yes) or in the 64-bit registry (no) on 64-bit clients

The second category contains custom scriptable detection rules. That is the most advanced rule format. That rule format enables the administrator to create detection rules that can check on basically anything that can be scripted, as long as the script has the correct output. A detection rule of that type requires the configuration properties as mentioned below. This rule type has some similarities with the Script rule type within the requirement rules. The main difference is with the output of this rule type as it’s more limited. In this rule type the detection of the Win32 app is based on the execution success of the script in combination with any output. It doesn’t matter what the output is.

  • Script name – This property enables the administrator to provide a name for the script.
  • Script file – This property enables the administrator to select a script that will be used to detect the installation of the app. When the script exit code is 0 and STDOUT contains any data, the app is detected (see table below for a summary).
  • Run script as 32-bit process on 64-bit clients – This property enables the administrator to configure the script to run in a 32-bit process (yes) or in a 64-bit process (no) on 64-bit clients.
  • Enforce script signature check – This property enables the administrator to configure that the script signature should be verified (yes) or that the signature verification should be skipped (no).
Exit codeData read from STDOUTDetection state
0EmptyNot detected
0Not emptyDetected
Not zeroEmptyNot detected
Not zeroNot EmptyNot detected

Administrator experience

Let’s end this post by having a look at the behavior of custom script detection rules on a Windows 10 device. The most advanced option. To do that I’ve used a really simple script that will detect the installation of Foxit Reader by looking at a specific directory. That can also be achieved by using a File rule type, but it’s an easy example for showing the functionality of custom script rule types. When the specific path is found, the script will output “Found it!“. That means that the detection rule will provide an output, when the detection was successful.

if (Test-Path "$($env:ProgramFiles)\Foxit Software\Foxit Reader\FoxitReader.exe") {
    Write-Host "Found it!"
}

When adding this script as a detection rule to a Win32 app and deploying that app as a required app to a user or a device, the installation process can be followed very good in the IntuneManagedExtension.log. That includes the process of detecting the installation of the app by going through the detection rule(s). Below is that example. It walks through the process of checking the detection rule(s) of the Win32 app. It shows the start of the script, the result of the script and following the detection state of the Win32 app (based on the result of the detection rule).

More information

For more information about the Win32 app functionality in Microsoft Intune, refer to the documentation about Intune Standalone – Win32 app management.