Block personally owned devices in Intune with enrollment restrictions
08-29-2021 3:18 PM

BEFORE YOU BEGIN

Disclaimer: All information and content in this blog posts is provided without any warranty whatsoever. The entire risk of using this information or executing the provided content remains with you. Under no circumstances should Dell, Microsoft, its author, or anyone else involved in the creation of these blog posts be held liable for any damage or data loss.
This blog post was originally written by me for my employer MINDCORE and an agreement between us allows me to re-post it on my own blog - Please visit the MINDCORE BLOG

Introduction

Today I will be looking at enrollment restrictions in Intune, which is a method to block personally owned devices. Did you know that all users (with an Azure AD P1 and Intune license) in your Azure AD by default is allowed to enroll (Azure AD join) their devices into Intune, they will then get all of your company configuration and local admin permission on the device. So, with that in mind and looking from a security point of view, I would not recommend that all users can enroll their own devices, and I think that every organizations should consider which devices can be enrolled into their Intune environment. I will show you how to restrict the enrollment of personally owned Windows devices for all users, but still make it possible for a few trustworthy users (e.g. IT staff)

Requirements

First some important knowledge

Before I show you how to restrict the enrollment of personally owned devices for all users, it is important to know a few things first. Like for instance that there are two types of device ownership in Intune:
Personal devices - These devices are registered in Azure AD (Azure AD registered) and enables the user to access your organizations Azure AD controlled resources - Bring your own devices (BYOD) Corporate devices - These devices are joined to Azure AD (Azure AD joined) and enables the user to access both cloud and on-premises apps and resources - Corporate-owned devices (COD) Visit the Microsoft Docs to read more about Azure AD joined devices and Azure AD registered devices
Block personally owned devices in Intune
There are two locations from where you can restrict device enrollment. The first location is device settings in Azure AD, which is like a main switch it's either on or off. In device settings it is not possible to distinguish between users/type/version etc. Or create multiple groups with different settings - the field “Users may register their devices with Azure AD” will be grayed out and set to “All” when Intune is configured in your tenant. Note. If you haven't configured Intune in your tenant, this is where you can restrict users from Azure AD join their devices.
Block personally owned devices in Intune
The other location is enrollment restrictions in Intune, from here you will be able to distinguish between users/type/version etc. And create multiple groups with different settings - which I will demonstrate further down in this blog post.
Block personally owned devices in Intune
It's also important to know that if you block personally owned Windows devices from enrollment, Intune checks to make sure that each new Windows enrollment request has been authorized as a corporate enrollment. Unauthorized enrollments will be blocked. The following methods qualify as being authorized as a Windows corporate enrollment:
  • The enrolling user is using a device enrollment manager account
  • The device enrolls through Windows Autopilot
  • The device is registered with Windows Autopilot but isn't an MDM enrollment only option from Windows Settings
  • The device's IMEI number is listed in Device enrollment > Corporate device identifiers
  • The device enrolls through a bulk provisioning package
  • The device enrolls through GPO, or automatic enrollment from Configuration Manager for co-management
The following enrollments are marked as corporate by Intune. But since they don't offer the Intune administrator per-device control, they'll be blocked:
  • Automatic MDM enrollment with Azure Active Directory join during Windows setup *
  • Automatic MDM enrollment with Azure Active Directory join from Windows Settings *
The following personal enrollment methods will also be blocked:
  • Automatic MDM enrollment with Add Work Account from Windows Settings *
  • MDM enrollment only option from Windows Settings
* These won't be blocked if registered with Autopilot. Source: Microsoft Docs

Block personally owned devices

By default all users can enroll their devices.
Block personally owned devices in Intune
As you can see in the below picture, Annie (my wife) was able to Azure AD join her device.
Block personally owned devices in Intune
But since I do not trust her social media infected devices - let's change that possibility. Go to https://endpoint.microsoft.com
Note. In a production tenant I would recommend that you create a new "Device type restriction" policy and leave the default policy untouched.
Click on “Devices” and select “Enrollment restrictions” from the “Policy” section. Select “All Users” in the name column for the default policy.
Block personally owned devices in Intune
Click on “Properties” and select “Edit
Block personally owned devices in Intune
In this demonstration I have blocked the “Android device administrator” platform because Google is deprecating device administrator support in new Android releases. I will recommend the modern and more secure device management “Android Enterprise (work profile)” and then I've blocked all personally owned devices for all users by default. Click “Review + save
Block personally owned devices in Intune
Click “Save
Block personally owned devices in Intune
Now that I have blocked personally owned devices in my default policy, we should only be allowed to Azure AD register our devices. Let's switch back to our two Windows 10 devices and confirm that it actually work. First I will try to Azure AD register my device (SUNE-PC) which should still work. Go to “Windows Settings” and click on “Accounts
Block personally owned devices in Intune
Click on “Access work or school” and select “Connect
Block personally owned devices in Intune
Enter your “email address” and click “Next
Block personally owned devices in Intune
Click “OK
Block personally owned devices in Intune
Click “Done
Block personally owned devices in Intune
Success! - Managed by mddprov account. My device is now Azure AD registered.
Block personally owned devices in Intune
Let's try to Azure AD join my wife's device (ANNIE-PC) and confirm that it is now being blocked. Go to “Windows Settings” - “Accounts” - “Access work or school” and select “Connect” Click on “Join this device to Azure Active Directory” and click “Next
Block personally owned devices in Intune
Enter your “email address” and click “Next
Block personally owned devices in Intune
She will still be prompted to join the organization. Click “Join
Block personally owned devices in Intune
Oh, something went wrong. Awesome! - bye bye social media infected devices.
Block personally owned devices in Intune
But she will still be able to Azure AD register her devices, which is OK.
Block personally owned devices in Intune
Some might then ask - But what will happen if you configure your mail and forget to uncheck “Allow my organization to manage my device”? Well, let's test it… So as you can see in the below GIF it will only Azure AD register your device.
Block personally owned devices in Intune
If you are happy with just blocking all personally owned devices in Intune - read no further. But keep on reading if you want to know how to allow personally owned devices for trustworthy users (e.g. IT staff)

Allow personally owned devices for trustworthy users

Okay, so we have now successfully blocked all personally owned devices by default, mine included! But I want to allow myself to Azure AD join my devices (because I'm that trustworthy IT guy…)
Block personally owned devices in Intune
Go to https://endpoint.microsoft.com Click on “Groups” and then click “New group
Block personally owned devices in Intune
Select “Security” as group type and give it a friendly group name and description (optional). Select “Assigned” in membership type and select members. Click “Create
Block personally owned devices in Intune
Here you can see properties and membership for my security group.
Block personally owned devices in Intune
Block personally owned devices in Intune
Now that we have created a security group with my account added to it, we then need to create a new enrollment restriction policy that allow personally owned devices. Click on “Devices” and select “Enrollment restrictions” from the “Policy” section. Click on “Create restriction” and select “Device type restriction
Block personally owned devices in Intune
Give the policy a friendly name and description (optional) Click “Next
Block personally owned devices in Intune
Block the “Android device administrator” platform like we did earlier in the default policy and click “Next
Block personally owned devices in Intune
Click “Next
Block personally owned devices in Intune
Add the newly created security group and click “Next
Block personally owned devices in Intune
Click “Create
Block personally owned devices in Intune
Block personally owned devices in Intune
It is also possible to limit the amount of devices which can be enrolled by a user by simply click on “All Users” for the default policy or add a new policy for the newly created security group. By default this limit is set to 5 and the max is 15 devices.
Block personally owned devices in Intune
Let's switch back to my Windows 10 device (SUNE-PC) and confirm that I'm able join it to Azure AD. Go to “Windows Settings” - “Accounts” - “Access work or school” and select “Connect” Click on “Join this device to Azure Active Directory” and click “Next
Block personally owned devices in Intune
Enter your “email address” and click “Next
Block personally owned devices in Intune
Click “Join
Block personally owned devices in Intune
Success! - Managed by OSDSune.Mindcorelab.
Block personally owned devices in Intune
Block personally owned devices in Intune
In Azure AD we should see that Annie's device is Azure AD registered and my device is Azure AD joined and managed by Intune.
Block personally owned devices in Intune
And from Microsoft Endpoint Manager admin center we should see that Annie wasn't able to enroll her device as personal. Go to https://endpoint.microsoft.com Click on “Home” and select “Device enrollment
Block personally owned devices in Intune
Block personally owned devices in Intune
We can also confirm the result by running this command line locally on the devices.
1
dsregcmd /status
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Block personally owned devices in Intune
Block personally owned devices in Intune

Summary

That's it folks. Now you know how to block personally owned Windows devices in Intune, but still allow a few trustworthy users to Azure AD join their devices. I've explained a few important information's and shown you how to confirm and check the results. Happy testing! If you have any questions regarding this topic, feel free to reach out to me. I am most active on Twitter!