Microsoft Teams: File sharing enabled by default in external (federated) chats

🚨 The Signal: Microsoft Teams will enable file sharing in external chats by default, automatically assigning permissions. This simplifies cross-organization collaboration but increases the risk of unintended data exposure if not managed.

The Impact

Organizations using Teams external access are affected, facing increased risk of data oversharing if existing controls are not reviewed.

  • Security Teams: Increased risk of data oversharing to external parties.
  • Admins: Default setting change requires review of existing external sharing policies.
  • Users: Easier file sharing externally, but potential for accidental data exposure.
  • Compliance Teams: Need to re-evaluate external collaboration policies against ISM/PSPF.

The Action

  1. Review existing external sharing policies for OneDrive and SharePoint to ensure they align with your organisation's risk appetite.
  2. Utilise PowerShell cmdlets to disable file sharing in external chats if not desired: Set-CsExternalAccessPolicy -Identity Global -EnableFileSharingInExternalChats $false
  3. Configure sensitivity labels and Data Loss Prevention (DLP) policies to protect sensitive information shared externally.
  4. Educate users on responsible external file sharing practices and the risks of oversharing.
  5. Regularly audit external sharing activities through Microsoft Purview audit logs.

Domain: Teams · Impact: high · Workload: Teams