The first enhancement introduces sophisticated malicious URL detection capabilities that can identify and warn users about potentially harmful links shared in chats and channels. This real-time protection system provides an additional layer of defense against malware attacks that commonly exploit seemingly innocent web links.
The second major improvement focuses on dangerous file type blocking. Teams now actively blocks messages containing weaponizable file types, including executables and other potentially harmful file formats, across chats and channels. This proactive approach significantly reduces the risk of malware distribution and other file-based security attacks within the platform.
Both security features are scheduled to begin their worldwide rollout across standard Microsoft 365 multi-tenants starting in September 2025, marking a substantial step forward in Teams’ security posture.
Established Protection Mechanisms
Beyond these new features, Microsoft Teams has already integrated comprehensive security measures through Microsoft Defender for Office 365. The Safe Links feature provides crucial time-of-click protection by checking URLs against a database of known malicious links whenever users click them within Teams. When a threat is detected, users receive a warning page in their default web browser, preventing potential security breaches.
This protection extends across both Teams desktop and web instances, ensuring consistent security regardless of how users access the platform. Notably, the system maintains user experience by not rewriting URLs, instead performing security checks only when links are actively clicked.
Comprehensive File Security
The Safe Attachments feature for SharePoint, OneDrive, and Microsoft Teams provides another crucial layer of protection against harmful files. This sophisticated system opens suspicious files in a secure virtual environment to analyze their behavior through a process known as detonation. The system can even examine password-protected files for known malicious patterns, providing comprehensive threat detection capabilities.
When malicious files are identified, the system immediately locks them using direct integration with file stores. While users can still see these files listed in their team sites and document libraries, they cannot open, copy, move, or share them, though deletion remains possible for cleanup purposes.
Advanced Administrative Controls
Microsoft has also introduced powerful administrative tools through integration with the Microsoft Defender for Office 365 Tenant Allow/Block List. Security administrators can now block incoming communications from specific domains, including chats, channels, meetings, and calls. The system goes further by automatically deleting existing communications from users in blocked domains, providing comprehensive threat mitigation capabilities.
These administrative controls reached general availability worldwide by late September 2025, giving organizations greater control over their Teams security environment through the centralized Microsoft Defender portal.
Additional Security Innovations
The platform has implemented several other noteworthy security features designed to address evolving cyber threats. Chat brand impersonation protection helps alert users to phishing attacks that specifically target organizations with external Teams access, a growing concern as remote collaboration increases.
For particularly sensitive communications, Teams now offers a “Prevent Screen Capture” feature for meetings. This capability turns the meeting window black if someone attempts to take a screenshot, providing an additional layer of protection for confidential discussions and presentations.
