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Laying the Foundation for New Collaboration Scenarios Like Teams Shared Channels
Updated: March 22, 2022
On February 7, Microsoft announced that Azure AD cross-tenant collaboration settings are available in preview. Part of Azure AD B2B Direct Connect, Azure AD cross-tenant access means that users can authenticate in their home tenant and use the credentials gained there to access resources in other tenants, subject to the collaboration settings now in preview. Microsoft says that the new settings allow organizations to control how users collaborate with other Azure AD organizations (Microsoft 365 tenants). Inbound and outbound controls are available to control access on a tenant-wide, group, or application basis, together with the ability to trust security claims from external organizations like multi-factor authentication and device compliance.
External Identities Settings
The new settings are available in the External identities section of the Azure AD admin center. The organizational settings tab is where you define settings for individual Azure AD tenants you want to collaborate with (Figure 1) while the default settings tab is where you define settings to apply to Azure AD tenants in general. Specific settings for another tenant take precedence over the default settings.
Being able to define how individual tenants interact with your tenant allows precise control over who can connect and what they can do. For instance, in Figure 2 we see that the inbound access settings for the O365Maestro tenant allow collaboration via just one application (Office 365). You can add other Microsoft applications to the mix or include other applications if registered in Azure AD.
Note the external users and groups tab. By default, any user can connect with your organization. If you don’t want this to happen, the inbound access settings allow you to define exactly whom from another organization can collaborate with people in your organization. Likewise, the outbound access settings give you control over the people in your organization you want to collaborate outside your tenant. Again, because the whole idea of collaboration is to enable people to work together, the default is to allow everyone to collaborate with external organizations. However, sometimes control is necessary, and you might want to manage who connects with specific tenants, and this is where you can exert that control.
Accepting Security Claims
All Azure AD organizations apply the same fundamentals of authentication to allow users access to resources. It therefore makes sense to accept that a process performed for one tenant is valid for connection to another. If your security posture is higher (for instance, your tenant insists on connections from trusted devices), you can still insist that external connections meet this standard while at the same time accepting valid claims established when users sign into the other organization.
The Trust settings tab defines the set of security claims made by another tenant you are willing to accept. For example, let’s assume that the other tenant enforces MFA for all users. The trust settings for the tenant allows you to accept that the tenant has validated the user’s identity with MFA and won’t issue another challenge from your tenant. Reducing the necessity for multiple MFA challenges removes a major source of user irritation. By default, Azure AD accepts connections from another tenant based on that tenant’s assessment of MFA, compliant (trusted) devices, and hybrid Azure AD joined devices. You can enable or disable each of these claims as shown in Figure 3.
Removing some friction from MFA challenges is a good thing. According to Microsoft, Azure AD customers secure only 22% of Azure AD accounts with MFA. That’s a horrible statistic (albeit showing steady growth over the past few years). The simple fact is that MFA helps accounts resist 99% of brute-force attacks designed to crack passwords, so this is an area where Microsoft 365 tenants need to do better.
If you don’t define settings for an Azure AD organization you want to collaborate with, Azure AD uses the default settings (Figure 4). Like those for individual tenants, the settings break down into B2B collaboration and Trust.
More information about configuring default and specific organization settings for cross-tenant access is available online. Like conditional access policies, it will take time to figure out the best approaches for configuring rules for inbound and outbound access. And like conditional access policies, no one wants to make the mistake of applying a change that blocks collaboration for everyone in a tenant. The advice is therefore to go slowly and understand exactly what effect a proposed change will have on users before proceeding.
Teams Connect the First for Cross-Tenant Access
Microsoft has said that people can connect using “native identities” to collaborate Teams shared channels (aka Teams Connect). It’s therefore no secret that Azure AD cross-tenant access is the foundation to allow users to use credentials obtained within their home tenant to connect with people in a shared channel in an external organization.
Teams shared channels (aka Teams Connect) are now in public preview. Many criticized Microsoft’s slowness in delivering shared channels but given that the feature depends on a new way of authentication and Azure AD collaboration that is only just available in preview, it’s understandable why the delay happened. After all, you don’t want authentication from another tenant to potentially compromise sensitive information stored in a shared channel. Teams Connect is likely the first app to exploit cross-tenant access. I don’t think it will be the last.
Azure AD cross-tenant access won’t mean that guest accounts will go away anytime soon. Many valid scenarios exist to demonstrate the usefulness of guest accounts. Cross-tenant access gives organizations a new way of collaborating to add to the methods enabled by guest accounts. It’s all goodness.
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