Find Out Who’s Using Teams Shared Channels in Another Tenant

Use Inbound and Outbound Shared User Profiles to Reveal the Ins and Outs of Membership in Teams Shared Channels

In August 2022, I discussed how to use the Get-AssociatedTeam cmdlet to report the membership of channels in teams for users within a tenant. It’s a useful cmdlet that includes the ability to report membership of shared channels in other tenants. In most cases, the reports that can be generated from the data returned by the Get-AssociatedTeam cmdlet meet the needs of administrators to know what channels users access.

Microsoft 365 often offers multiple ways to report data. In this instance, Azure AD supports shared user profile resources created for use with Azure AD B2B Direct Connect, the underlying cross-tenant access mechanism for shared channels.

• An inbound shared user profile represents an Azure AD user from an external Azure AD tenant whose profile data is shared with your tenant. The profile data is used by applications like Teams to display information about the inbound user in shared channels.
• Conversely, an outbound shared user profile represents Azure AD users from your tenant who share their profile information when they access resources in other Azure AD tenants.

Essentially, when a shared channel owner invites an external user to become a member of the channel and that user confirms their acceptance, Azure AD creates an inbound shared user profile to note this fact. Azure AD creates an outbound shared user profile when a user from your tenant becomes a member of a shared channel hosted by another tenant. For example, Figure 1 shows the membership of a Teams shared channel. The users marked with (External) have inbound shared user profiles.

Using PowerShell to Report Shared User Profiles

The Microsoft Graph PowerShell SDK contains cmdlets to fetch information about unbound and outbound user profiles. With consent for the CrossTenantUserProfileSharing.Read.All permission, you can connect to the Graph and run these commands:

Connect-MgGraph -Scopes CrossTenantUserProfileSharing.Read.All
Select-MgProfile beta
Get-MgDirectoryOutboundSharedUserProfile

UserId
------
08dda855-5dc3-4fdc-8458-cbc494a5a774
5b52fba5-349e-4624-88cd-d790883fe4c4
a221d10f-e0cf-4a1d-b6a2-4e844670f118
cad05ccf-a359-4ac7-89e0-1e33bf37579e
eff4cd58-1bb8-4899-94de-795f656b4a18

The output is a list of identifiers for Azure AD user accounts, so it’s not very exciting. IApart from not listing account names, the output doesn’t tell us what outbound tenants are accessed. To get that information, we must run the Get-MgDirectoryOutboundSharedUserProfileTenant cmdlet for each account. The output of that cmdlet is a list of tenant identifiers, which we can resolve to discover the tenant name. Here’s the code:

[array]$Users =  Get-MgDirectoryOutboundSharedUserProfile | Select-Object -ExpandProperty UserId
ForEach ($User in $Users) {
   $UserData = Get-MgUser -UserId $User
   [array]$TenantNames = $Null; $TenantDisplayNames = $Null
   [array]$TenantIds = Get-MgDirectoryOutboundSharedUserProfileTenant -OutboundSharedUserProfileUserId $User | Select-Object -ExpandProperty TenantId
   If ($TenantIds) {
       ForEach ($TenantId in $TenantIds) {
         $Uri = ("https://graph.microsoft.com/beta/tenantRelationships/findTenantInformationByTenantId(tenantId='{0}')" -f $TenantId.ToString())
         $ExternalTenantData = Invoke-MgGraphRequest -Uri $Uri -Method Get  
         $TenantNames += $ExternalTenantData.DisplayName
       }
       $TenantDisplayNames = $TenantNames -join ", "    
   }
   Write-Host ("User {0} has outbound shared profiles in these tenants {1}" -f $UserData.DisplayName, $TenantDisplayNames)
}

User Sean Landy has outbound shared profiles in these tenants o365maestro
User Ken Bowers has outbound shared profiles in these tenants o365maestro
User Tony Redmond has outbound shared profiles in these tenants o365maestro, Microsoft Community & Event Tenant

Getting Inbound Shared User Profiles

The Get-MgDirectoryinboundSharedUserProfile cmdlet lists information stored about inbound shared user profiles. We can’t read Azure AD to find information about these users because they come from other tenants. This is what the cmdlet returns:

Get-MgDirectoryinboundSharedUserProfile | Format-List

DisplayName          : Alex Wilber
HomeTenantId         : 22e90715-3da6-4a78-9ec6-b3282389492b
UserId               : a6453657-2058-4c15-a38a-b0a94f0ed737
UserPrincipalName    : AlexW@o365maestro.onmicrosoft.com
AdditionalProperties : {}

Once again, we can resolve the tenant identifier to make the information more understandable:

[array]$Guests = Get-MgDirectoryinboundSharedUserProfile
ForEach ($Guest in $Guests) {
    $Uri = ("https://graph.microsoft.com/beta/tenantRelationships/findTenantInformationByTenantId(tenantId='{0}')" -f $Guest.HomeTenantId.ToString())
    $ExternalTenantData = Invoke-MgGraphRequest -Uri $Uri -Method Get  
    Write-Host ("User {0} comes from tenant {1}" -f $Guest.DisplayName,  $ExternalTenantData.DisplayName)
}

User Christina Smith comes from tenant CM Portal Solutions
User Nicolas Blood comes from tenant NBConsult
User Alex Wilber comes from tenant o365maestro
User Tom Jones comes from tenant o365maestro
User Vlad Bitton comes from tenant vNext Solutions

The interesting thing here is that I didn’t recognize some of the user names and tenants that Azure AD stored inbound shared user profiles for. However, given that the names were all MVPs and my tenant supported many beta versions of Teams shared channels in the past, it’s entirely possible that the profiles originated in a test. Azure AD doesn’t register a date to tell you when it created a profile, so there’s no clue from that source.

Tracking External Access to Teams Shared Channels

My previous article describes how to create a report about the users accessing shared channels in your tenant. The added piece of information covered here is finding the set of Azure AD accounts from your tenant who use Azure AD B2B Connect to access resources in other tenants. That’s a valuable nugget if you want to track who’s interacting with Teams shared channels externally.