Microsoft has announced significant security enhancements for Teams, introducing robust protections against malicious file types and dangerous URLs.
In a dual-pronged update, Microsoft will automatically block potentially dangerous executables and warn users about malicious URLs in chats and channels.
“Microsoft Teams now blocks messages containing weaponizable file types, such as executables, in chats and channels, increasing protection against malware and other file-based attacks,”
Microsoft said in a roadmap update.
“Microsoft Teams can now detect and warn users on malicious URLs sent in Teams chat and channels,” it added in a separate entry.
These security improvements represent Microsoft's comprehensive and company-wide efforts to address fundamental vulnerabilities in its security posture, although some question why this update was not implemented sooner.
Microsoft’s Comprehensive Security Overhaul
The security update marks a shift in how Microsoft Teams handles potential threats, implementing automated detection and blocking mechanisms at the platform level.
Microsoft’s roadmap entries 499892 and 499893 detail that Teams will now scan both file attachments and embedded URLs for malicious content before they reach users.
Files containing executables can, once clicked, instruct a computer or platform to run a certain program, potentially downloading malware or Trojans. URLs can lead users to sites that deliver malware to their computers.
This proactive approach minimizes the human factor that has made Teams users vulnerable to social engineering attacks, where legitimate-looking attachments or URLs contain malicious payloads designed to compromise corporate networks.
Additionally, Microsoft announced in the Microsoft 365 Message Center that Teams now integrates with the Microsoft Defender for Office 365 Tenant Allow/Block List. This enables security administrators to block incoming communications (chats, channels, meetings, and calls) from blocked domains, automatically delete existing communications from users in blocked domains, and manage blocked external domains in Microsoft Teams via the Microsoft Defender portal.
Such control eliminates the ability for malicious files or URLs to remain within a system long after they are identified.
All features are due to roll out by late September 2025. Despite this seemingly imminent rollout, hackers have long exploited executables in Teams.
The Growing Threat Landscape in UC
Teams has become a prime target for sophisticated threat actors due to its central role in modern business communications.
Increasingly, more business-critical information is being shared on these platforms, yet its security is seen as a weak spot for gaining wider entry into company networks.
Cybersecurity researchers have documented increasingly creative attack methodologies that exploit the platform’s collaborative features.
