What is the primary security consideration when deciding whether to use guest access versus external access in Microsoft Teams?

The primary security consideration when deciding between guest access and external access in Microsoft Teams revolves around the level of control and auditing capabilities your organization requires over the external user's activities and data access. Guest access provides a higher degree of control. Guests are added to your organization's Azure Active Directory (Azure AD) as guest users, allowing you to apply conditional access policies, multi-factor authentication (MFA), and data loss prevention (DLP) policies to them, just as you would for internal users. Their activities are also more thoroughly logged and auditable within your Azure AD environment. External access (also known as federation) allows users from other organizations to participate in Teams meetings and chats without being added as guests to your Azure AD. This offers less administrative overhead but provides significantly reduced control and auditing capabilities. You cannot enforce MFA or DLP policies on federated users, and their activities are not as comprehensively logged within your environment. For example, if you need to ensure that external users accessing sensitive data are subject to the same security controls as internal users (e.g., requiring MFA), guest access is the appropriate choice. If you only need to collaborate with external users on non-sensitive topics and require minimal administrative overhead, external access might be sufficient. The decision depends on a risk assessment that balances ease of use with the need for robust security and compliance.