Microsoft Issues Urgent Security Guidance as Teams Faces Surge in Cyberattacks

Microsoft is sounding the alarm on a growing wave of cyberattacks targeting its Teams platform, publishing its most detailed security guidance yet as threat actors increasingly exploit workplace collaboration tools.

The company’s new advisory focuses on how attackers are using Teams chats, channels, and linked OneDrive and SharePoint data to infiltrate organizations. Microsoft says the goal is to help IT teams detect and respond to attacks before they spread across integrated Microsoft 365 environments.

Security researchers have identified multiple ongoing campaigns that validate Microsoft’s concerns. One, known as Oyster, uses malicious advertisements and poisoned search results to trick users into downloading fake Teams apps.

Another sophisticated operation has reportedly infiltrated over 900 organizations by disguising spyware inside fake Zoom and Teams meeting invites. Cybersecurity firm Trend Micro has also detailed a campaign that begins with Teams impersonation and ends with backdoor malware installation through DLL sideloading..

Microsoft’s latest guidance warns that protecting Teams requires a multi-layered approach spanning identity, endpoint, and network defenses. The company highlights red flags such as unusual meeting invites, rapid-fire chat activity across multiple users, suspicious bot behavior, and unexpected data access patterns.

Once seen as purely productivity tools, platforms like Teams have now become central to corporate cybersecurity strategy. Microsoft’s message is clear: organizations that fail to secure real-time collaboration risk exposing their most sensitive business data.

via: UC Today