Intune - Detection and Remediation scripts for BitLocker key escrow to Entra-AD (Azure AD / AAD)

Credit where it is due, I got most of this from Jonathan Conway's blog post at https://jonconwayuk.wordpress.com/2022/08/11/intune-proactive-remediation-bitlocker-key-escrow-to-azure-ad-after-mecm-osd-task-sequence

Detection Script:

What should your secure MFA solution look like?

 I have run across many "MFA" implementations that are only providing a false sense of security because they aren't actually MFA at all.  After the most recent one, which had to do with income and financial documents I decided to write up a blog post so that I can share it with people to help them understand.  Even though I am writing this to help people fix bad MFA implementation, hopefully at least a few readers will find this useful to set up MFA properly in the first place.

First, what is MFA?  MFA stands for multi-factor authentication.  The consensus is that there are only three possible factors that you can work with, so you MFA means that you MUST use at least two of these factors to access whatever it is that you are attempting to access.  The three possible factors are:

1. Something you know (like a password)
2. Something you have (a physical item like a security key card, a company laptop, a specific cell phone, etc)
3. Something you are (biometrics like fingerprints, voiceprint, retinal scan, etc)

We've all seen in movies where someone has to use both a key card and a hand scanner to enter an area... that's MFA.  A password followed by a voiceprint, also MFA.  A password then authentication using an app on your phone, that's MFA.

The problem, where most people mess it up, is the "MUST" in the definition.  Often "MFA" (when I put that in quotes it is the false sense of security and not truly MFA)... often "MFA" is set up to require a password and then has an option for the second factor to be an email, a text, or an authenticator app.  Seems fine on the surface but let's look closer at how people actually use email, texts, and cell phones (authenticator apps)...  Here's an example scenario:

1. A bad actor lifts a cell phone off the table at a local coffee shop while its owner is up getting their latte.  The owner didn't bother to lock the phone (which is why it was an ideal target for this bad actor) so as long as the thief keeps touching the screen every couple minutes it will never lock.
2. The thief scrolls through the email on the cell phone and finds a link to an financial website (that is supposedly protected by MFA).
3. The thief goes to the portal and finds that the username is an email address, so they use the email address of the account on the phone and select the "forgot password" link.
4. Ding!  The phone gets a reset password email from the portal website.  The thief resets the password and attempts to log in.
5. The thief is now presented with the "MFA" prompt, would they like to authenticate with:
• An Email message
• A text message
• An authenticator app
  
6. The thief chooses "an email message" because they know that they have the email account, though likely a text message would come right to this phone and also likely the authenticator would as well.
7. Ding! The thief gets the email for "MFA" and logs into the financial site.
8. The thief proceeds to buy a bunch of cryptocurrency with the victims money and the disperse that into their laundering crypto-wallets.

This scenario works no matter how the victim's email account is compromised.  The scenario shows that there is only 1 factor, the user's email account.  Everything else is window dressing to give a false sense of security.  I see this repeated over, and over, and over.

In this scenario, simply having the user's logon name not be the email address AND blocking storage of that logon name in the browser might have prevented the theft.  I say "might" because the major underlying problem is using the primary email account as a recovery method.  If the attacker were able to click a "forgot username" link and get the username sent to that primary email address, they are still able to pull off the attack.

The fix is pretty simple... allow the option for a "recovery email address" that is separate from the email address used for normal correspondence.  Sure, many users will not avail themselves of the option, but that is on the user and not on you as the provider of the MFA system.

Also, not all authenticator apps are equal.  Only allow ones that require a second factor (preferably biometric, like fingerprint scan on the smartphone) before it will present the code/authentication item.

As of the time of this writing:

• Apple Passwords has an option to require a fingerprint, PIN or password when you open the app or approve a notification and it is on by default on iDevices.
• Google Authenticator has an option to require a fingerprint, PIN or password when you open the app or approve a notification and it is on by default on Android devices.
• Microsoft Authenticator has an option to require a fingerprint, PIN or password when you open the app or approve a notification.
• Okta Verify does not have an option to require a fingerprint, PIN or password before displaying the authentication code.  So, the scenario above would work just fine for the attacker if the authenticator app was SecurID.
• SecurID does not have an option to require a fingerprint, PIN or password before displaying the authentication code.  So, the scenario above would work just fine for the attacker if the authenticator app was SecurID.
• Symantec VIP Access does not have an option to require a fingerprint, PIN or password before displaying the authentication code.  So, the scenario above would work just fine for the attacker if the authenticator app was SecurID.

So, yeah, the scenario could have been thwarted if an authenticator were required, provided it was one of the big three providers, AND, big and here... the account recovery email address was different than the correspondence email address.  If the account recovery (not just password recovery. but account recovery) is on that primary email address then the attacker clicks the "recover my account", gets the email, and resets the MFA to either turn it off or uses their own phone to create a new one.  So again, the major underlying problem is using the primary email account as a recovery method.  In order to provide security to your clients you must give them the option to set a different email account as the recovery account.

So... what should your secure MFA solution look like?

1. The user should be able to set up a second email account for any/all recovery options.  This is the most common mistake that I see made across "MFA" solutions.
2. The user should choose an MFA solution (text/email/app/etc) at the time of their account setup and the other options should not be available during normal logon.  Either use the one that was set up or use a recovery option.  This is the second most common mistake that I see; what is the point of me setting up an authenticator app if you are still going to offer the would-be attacker the option of getting an SMS text or an email?
3. A secure authenticator app (one that allows for that 2 factor on the phone) should be highly recommended during account setup.
4. Email address should not be used as a username (not precisely an MFA item, but a basic security principle).
5. Changing both the correspondence and recovery email addresses should be possible by the user.  Yes, I have actually seen quite a few sites that do not allow you to change your email address.  Usually the same ones that are using that email address as the logon.
6. Require re-validation of the MFA (check their credentials again) to display/change the recovery address.

If you get those six things right then I'm pretty sure everything else will fall into place and you will have an actual MFA solution, not a "email is the only factor" solution.

Setting Peer Download options for SCCM boundary groups using Powershell

 If you have more than just a few boundary groups you have probably wanted a way to quickly set these options across all of them.  I suggest setting the options for your VPN boundary group(s) first. For VPN you probably want to prefer cloud based sources and not use peer downloads at all (to prevent peering with internal computers).  Once you have that set then you can run this little gem to set all of the others for what I believe is the best settings.  Of course you can modify it if you think other settings are best.

Here you go:

<#
.Synopsis
   Set SCCM Boundary Group Peer Cache options to Allow peer cache downloads within this Boundary Group but restrict downloads to peers within the same subnet.
.DESCRIPTION
   Use this in order to quickly change the peer cache options for a set of boundary groups.  The more boundary groups you have
   in your organization, the more beneficial this becomes.
   The flags (at time of writing) that you will see in the boundary groups are:
   0 - Allow peer downloads in this boundary group (only first check box is checked)
   1 - Do not allow peer downloads in this boundary group (no check boxes are checked)
   2 - Allow peer downloads in this boundary group but During peer downloads only use peers within the same subnet (first two check boxes are checked)
   9 - Prefer cloud based sources over on-premises sources and Do not allow peer downloads in this boundary group (only last check box is checked)
   I have not experimented to find out what results come from other combinations of check-boxes.
#>

#Change testmode to false to save the changes
$testmode=$false

#The Configuration Manager site code
$sitecode="ABC"

#The Configuration Manager Primary Server
$SMSProvider="SCCMserver.domain.com"

#the flag you want to set
$newflag=2
$BoundaryGroups = (get-wmiobject -Namespace root\sms\site_$sitecode -Class SMS_BoundaryGroup -computername $SMSProvider) | Where-Object {($_.Flags -NE 2) -and ($_.Flags -le 2)}
Foreach ($BoundaryGroup in $BoundaryGroups) {
    write-host "Setting $($BoundaryGroup.name) flags to $newflag (previously $($BoundaryGroup.flags))"
    $BoundaryGroup.Flags = $newflag
    Try {
        If (-not $testmode) {
            $result=$BoundaryGroup.Put()
            write-host "saved" -ForegroundColor green
        }
    } Catch {
        write-host "failed to set flag" -ForegroundColor red
    }
}

Controlling SCCM bandwidth Utilization

 

There are four items that control network bandwidth utilization within SCCM: 

1. BITS client setting – The download of data from the distribution point to the client is a BITS download.  In the client settings of the clients the rate of those downloads can be adjusted.  However, this is client side and does not know about bandwidth on the network so if enough clients, even if all configured to 1Mbps, are trying to download at the same time it can still clog the WAN.
   https://learn.microsoft.com/en-us/mem/configmgr/core/clients/deploy/about-client-settings#background-intelligent-transfer-service-bits
   
   I recommend setting the BITS settings but to something that will work for your organization.  Exactly what that is varies greatly from one organization to another.
   
   
   

   
   
   
2. Rate Limit Schedules –  Set in the Distribution Point properties, this controls maximum data that can be sent to each distribution point  at any given time of day.  This is to prevent WAN saturation while getting the data onto the distribution points prior to deployment to clients.
   https://learn.microsoft.com/en-us/mem/configmgr/core/plan-design/hierarchy/manage-network-bandwidth#BKMK_PlanningForThrottling
   
   I recommend setting the rate limits but to something that will work for your organization.  Exactly what that is varies greatly from one organization to another.  Remember that this is set individually for each distribution point.
   
   
   
   
   
   
   

3. LEDBAT - Where BITS worked client side, LEDBAT works server side to control bandwidth usage.  Like the throttling rate limits it is enabled on each distribution point individually.  The idea is that it dynamically adjusts transfer rates so that clients only use network bandwidth when it's available.
   https://learn.microsoft.com/en-us/mem/configmgr/core/plan-design/hierarchy/fundamental-concepts-for-content-management#windows-ledbat
   
   I recommend turning this on for every distribution point.
   
   
   
   

4. Peer caching technologies – Peer caching takes at least a portion of the load off of the WAN by allowing clients to share cached deployment data with each other.  We would limit this to only peers that are on the same subnet in order to ensure that they are never going cross-WAN. There are three peer caching technologies available in SCCM.  Without going deep on all of them I will just say that the on I recommend using is “Peer cache” for on-premises and Delivery Optimization for cloud (Intune).  Yes, use both if you have both on-prem SCCM and Intune because Delivery Optimization gives no benefit to your Line-of-Business applications or anything else that is not delivered from Microsoft's global distribution network.
   https://learn.microsoft.com/en-us/mem/configmgr/core/plan-design/hierarchy/fundamental-concepts-for-content-management#peer-caching-technologies
   
   I suggest turning on Peer Cache for all non-VPN connected clients and enabling peer downloads, but limited to same subnet, on all non-VPN boundary groups.
   
   
   

   
   
   
   
   
   

Export all Scheduled Tasks

Unfortunately I've not yet figured out how to export the schedule itself, but for everything else run an elevated Powershell and: 

$outcsv = "C:\Users\$env:USERNAME\desktop\taskdef.csv"
Get-ScheduledTask |
ForEach-Object { [pscustomobject]@{
Name = $_.TaskName
Path = $_.TaskPath
User = $_.Principal.UserID
LastResult = $(($_ | Get-ScheduledTaskInfo).LastTaskResult)
NextRun = $(($_ | Get-ScheduledTaskInfo).NextRunTime)
Status = $_.State
Command = $_.Actions.execute
Arguments = $_.Actions.Arguments }} |
Export-Csv -Path $outcsv -NoTypeInformation

Get Number of Days since last Windows Udpate was applied

In order to pre-emptively identify computers that are not getting software updates you might want to know how long it has been since they last applied a Windows Update.  Here you go:

$TimeNow = Get-Date
$LastSUInstall = ((Get-WmiObject -Class win32_quickfixengineering -Namespace root\cimv2).InstalledOn | sort -Descending)[0]
[Int]$OutputInt = ($TimeNow.Subtract($LastSUInstall)).Days
Write-Output $OutputInt

Why using Windows Hello is less secure than not using it

Let's try a thought experiment...

You are guarding the gate of a castle.  That gate is the only way into the castle.  In order to enter via the gate a password is required.  When someone comes up to the gate, you challenge them, "PASSWORD!" and they respond either with the correct password or not.  Based on their response you either allow them entry or you don't.  The password to every royal estate is the same, so any noble-person that knows the password can enter every royal estate.

Some bandits got ahold of the password and began raiding the royal estates.  In response the king changed the password and then in order to increase security even further he had his masons put a hole in the castle wall and install another gate.  He placed another guard at the new gate and this guard was told to require a slip of paper, signed by the king, be presented to allow entry... a "certificate of entry".  The certificate only works at the one castle/computer, unlike the password which the king uses at every one of his estates.  

The king did not get rid of your gate, people can still enter using the (now changed) password but they can also enter through the other gate by presenting their certificate of entry.

Now... was the castle more secure when it only had one entry point or is it more secure now that it has two?  Obviously one entry point is more secure than two, but the king is hoping that using the certificates of entry will keep the bandits from plundering his other holdings as well.  If the bandits got ahold of a certificate of entry they can enter the castle and plunder it, but they cannot enter other royal estates.  That's good, it is keeping the other estates secure.  

So, soon the bandits did just that.  They intercepted a nobleman, stole his certificate of entry into the castle.  Once inside the castle, being smarter than the king had given them credit for, the bandits hid out near your gate and listened for the password.  They then ran amock plundering all of the estates again AND stealing more certificates of entry to those other locations as well.

Just like the second gate at our imaginary castle, Windows Hello opens up a second gate to any computer upon which it is used.  So, each and every one of those computers is less secure.  Just like the certificate of entry to our castle once Windows Hello is breached it can be reused to access that computer.

Now, unlike our imaginary castle, Windows Hello actually presents two gates itself; the PIN, or click-on-pic, or biometric that is used for the user interface and the certificate that is actually passed from the computer to the network.  This allows for two distinct avenues of attack.  If an attacker gets that certificate then they can replay it infinitely (because you cannot change it as the user) to access the network from that computer (not from just any computer, but who cares at that point).  The attacker could obviously get ahold of the PIN or Click-On-Pic combination just like normal shoulder surfing for passwords.  But the scariest of all is if the attacker subverts the biometrics.  Good luck changing your fingerprints or IR signature should an attacker be able to duplicate them.

Your password can always be used as a back up to Windows Hello.  So, Windows Hello is really just opening another hole in the wall.  If the attacker does get inside through Windows Hello, it is much easier to get the password from the inside than it is from outside.  Your password is stored (encrypted) on the device even if you are using Windows Hello and there is also a high probability that you will need to provide your password at some other gate and it can be intercepted when you do so.

That, my friends, is why using Windows Hello is less secure than not using Windows Hello.