Microsoft Teams to Let Admins Block Custom File Types in Weaponizable File Protection Upgrade

The feature has already been available in Teams, but until now it automatically scanned attachments for potential danger. The automated component began rolling out in early 2026 after an earlier preview listed on Microsoft's roadmap. The new roadmap entry adds administrative customization rather than replacing the automated scanning, allowing organizations to set their own block lists.

"Administrators will be able to customize which file types are blocked in Teams to align with their organization's security requirements or continue using the Microsoft-recommended default list," the roadmap entry says, according to TechRadar. That means admins can either keep Microsoft's default list or tailor restrictions to their own security policies.

Microsoft is aiming to deliver the capability in November 2026. Once available, administrators will have greater control over which file types are blocked across their organization. The roadmap entry does not specify which file extensions would be included in the Microsoft-recommended default list or how the custom lists would be managed.

The move follows a similar automated security step in Teams. About a year before the Sept. 21 report, Microsoft rolled out a feature that scanned links in Teams for potentially malicious intent. The link-scanning feature and the attachment-scanning tool reflect how security teams have tried to keep pace with attackers using collaboration platforms.

Microsoft has said Teams presents particular risks because its traffic often does not pass through the same secure email gateways that inspect email. In a separate security study, the company wrote: "Unlike email, Teams traffic typically bypasses secure email gateways and benefits from the perceived legitimacy of a colleague-initiated chat, which can make lures particularly effective in this environment." That dynamic has made Teams an attractive target for attackers, according to the study cited by TechRadar.

November is also set to bring other Teams changes. Roadmap entries point to simultaneous screen sharing for two presenters, breakout room support for Android, and a Meeting Shared Files window that would let users reach attachments from specific meetings more easily. Those features, like the file-blocking controls, are listed for future release rather than currently available.

Editor's Summary

Microsoft plans to add custom file-type blocking to Teams' Weaponizable File Protection, letting admins tailor restrictions beyond the current automated attachment scanning. The change is targeted for November 2026, when Teams is also scheduled to receive several collaboration features. Microsoft has said Teams traffic can evade secure email gateways, making the platform a growing target for attackers.