Microsoft Fixes Teams’ Major Flaw Exploited by Hackers

Microsoft has rolled out major security upgrades for Teams, introducing advanced safeguards to protect users from harmful file types and dangerous links.

In a dual-layered update, the company will now automatically block risky executable files and alert users about malicious URLs shared within 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 stated in a recent roadmap update.

“Microsoft Teams can now detect and warn users on malicious URLs sent in Teams chat and channels,” it added in another entry.

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Strengthening Microsoft’s Security Posture

This development reflects Microsoft’s broader efforts to close long-standing gaps in its security framework. While some critics argue that these protections should have been introduced earlier, the update demonstrates the company’s commitment to addressing fundamental vulnerabilities.

According to roadmap entries 499892 and 499893, Teams will now scan both attachments and embedded links before they reach end users. Executable files can instruct systems to run programs that often deploy malware or Trojans, while malicious URLs may redirect users to harmful websites. By tackling these risks at the platform level, Microsoft minimizes the human errors that cybercriminals frequently exploit through social engineering tactics.

Microsoft also shared via the Microsoft 365 Message Center that Teams now works with the Microsoft Defender for Office 365 Tenant Allow/Block List. This gives administrators stronger control by:

• Blocking incoming chats, meetings, and calls from potentially suspicious domains. 
• Automatically deleting harmful communications from previously blocked sources.
• Quickly manage blocked external domains directly within the Microsoft Defender portal. 
•  These measures ensure malicious content cannot linger in a system after being flagged. All features are expected to roll out by late September 2025.

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Escalating Threats Targeting Teams

The urgency behind these updates stems from the growing volume of attacks against collaboration platforms like Teams. As more sensitive business information flows through UC (unified communications) tools, cybercriminals view them as high-value gateways into corporate networks.

Security researchers have highlighted increasingly sophisticated methods targeting Teams. For instance, Storm-2372, a notorious hacking group, has exploited Microsoft’s OAuth 2.0 Device Authorization Grant via fake Teams meeting invites. This campaign, active since August 2024, has compromised government agencies, NGOs, and critical infrastructure worldwide.

Meanwhile, cybersecurity firm Check Point has tracked malicious executables circulating on Teams since 2022. These findings raised concerns about why Microsoft delayed acting on such a well-documented vulnerability.

The company’s push for stronger protections comes after a series of high-profile failures, including its CEO’s $5 million pay cut linked to security lapses. In response, Microsoft introduced the Secure Future Initiative to strengthen its cloud and enterprise security ecosystem.

How the New Features Mitigate Risks

Microsoft’s automated blocking of executables directly disrupts one of the most common attack vectors used to spread malware. By removing the need for employees to judge the safety of files or links, Teams eliminates the human factor that has often been the weakest link in cybersecurity.

The real-time scanning of URLs closes another critical gap by identifying dangerous links before users click on them. This is particularly valuable given that attackers like Storm-2372 often disguise links to appear legitimate while concealing credential theft or malware delivery schemes.

Moreover, Teams’ integration with Microsoft Defender ensures consistent security policies across both email and collaboration platforms, reducing opportunities for hackers to exploit gaps between communication channels.

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Securing the Future of Digital Collaboration

Microsoft’s overhaul of Teams security underscores the growing importance of protecting unified communication platforms from evolving cyber threats. Automated protections against malicious files and URLs reflect a recognition that awareness training alone cannot combat today’s highly engineered attacks.

By embedding Teams into the company’s larger security ecosystem, Microsoft signals a strategic shift—treating collaboration platforms as core security infrastructure rather than just productivity tools.

As organizations continue embracing hybrid and remote work, the resilience of tools like Microsoft Teams will play a decisive role in overall enterprise cybersecurity.

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