Adversaries are exploiting Microsoft Teams' default external chat functionality to conduct social engineering attacks and deliver malicious payloads. Analysis of over 400 incidents reveals threat actors consistently impersonate IT support personnel using throwaway Microsoft 365 tenants with IT-themed display names marked as "(Internal)" to bypass external-user warnings. Attacks frequently begin with email bombing followed by Teams contact offering assistance. Adversaries leverage legitimate remote monitoring tools like Quick Assist, AnyDesk, and ScreenConnect to gain hands-on-keyboard access, progressing from initial contact to payload execution in under 15 minutes. Infrastructure patterns show a shift from default onmicrosoft domains toward paid top-level domains, particularly .top domains comprising 50 percent of observed cases. The technique exploits legitimate collaboration features rather than software vulnerabilities, requiring organizations to implement allow-list policies and user training to disru...
Between January and April 2026, a coordinated social engineering operation named Spring Ring leveraged external Microsoft Teams accounts to impersonate IT help desk personnel, targeting over 150 employees across at least 10 companies. Adversaries initiated voice phishing calls to coerce victims into executing remote monitoring and management tools or custom malware. In advanced variants, attackers transitioned from vishing to NTLM relay attacks targeting domain controllers. Two distinct campaigns were observed: Campaign A utilized RMM tools and obfuscated PowerShell-based RATs, while Campaign B employed tailored cloud infrastructure with PetitPotam exploitation for domain-level compromise. The operation demonstrates the weaponization of trusted collaboration platforms as primary attack vectors, exploiting the trust gap in SaaS applications.
Since January 2026, a threat actor likely functioning as an initial access broker for ransomware operations has been targeting organizations through Microsoft Teams vishing attacks. Attackers impersonate IT helpdesk staff to convince victims to initiate Quick Assist remote sessions. Following initial compromise, PowerShell scripts deploy a Go-based backdoor called GoGRPC, which exists in four distinct variants: Lep, Giver, Pet, and Kind. These variants communicate with command-and-control infrastructure using gRPC over HTTP/2, an uncommon approach that helps blend malicious traffic with legitimate communications. Additional tools observed include BlindDoor backdoor, RevSocket and PyGRPC SOCKS proxies, S3Siphon data exfiltration utility, and RSOX Rust-based proxy relay. Recent campaigns show increased sophistication and selectivity, with heightened focus on corporate environments through enhanced PowerShell scripts capable of antivirus detection, domain controller fingerprinting, and system reconnaissance b...
In April 2026, threat actors deployed Nimbus RAT against a legal industry target using Microsoft Teams voice phishing. The attack began with email bombing (282 emails in 90 minutes), followed by a fake IT helpdesk contact via Teams who convinced the victim to grant Quick Assist remote access. Within 20 minutes, a Java-based RAT was deployed that uses Google Drive and Google Sheets for command-and-control, making network traffic appear benign. Analysis of 1,540 suspicious Teams messages across 172 customer environments over 12 months revealed 65% originated from throwaway onmicrosoft.com tenants with IT-themed names. The malware bundles its own Java runtime, implements two credential theft mechanisms, and allows in-memory second-stage code execution. Post-compromise targeting included Signal Desktop attachments and Outlook mailboxes.
An emerging threat group is conducting a global SEO-poisoning campaign distributing trojanized Microsoft Teams installers that deploy a multi-stage shellcode loader and backdoor designated Lorem Ipsum. Active since February 2026, the campaign targets users searching for Microsoft Teams across six countries, with confirmed targeting of a US healthcare organization. The operators evolved rapidly from minimally obfuscated test builds to sophisticated loaders featuring substitution cipher decoding, XOR-encrypted shellcode, DLL sideloading, and JFIF-disguised C2 traffic. The malware distinctively abuses letsdiskuss[.]com, a legitimate India-based platform, as a dead-drop resolver for C2 infrastructure. Attackers use validly signed MSI installers with three-day Microsoft ID Verified certificates, NameCheap-registered infrastructure weaponized within hours, and per-victim UUID-tracked callbacks. Development velocity suggests possible LLM-assisted tooling, indicating a well-funded mid-tier criminal actor operating...
In late February 2026, following escalating Middle East tensions and coordinated military actions, Iranian APT group Seedworm launched sophisticated social engineering attacks via Microsoft Teams. Attackers impersonated IT support personnel using deceptive Microsoft 365 tenant domains to convince victims to execute malicious MSI installers. The campaign deployed a custom backdoor called Dindoor, which leveraged legitimate Deno runtime to execute obfuscated payloads in-memory, minimizing detection. The operation included multiple components for persistence, command-and-control communications, and data exfiltration. Infrastructure overlapped with previously reported MuddyWater operations. The attack demonstrates the group's evolution in using collaboration platforms as initial access vectors while combining dual-use tooling with living-off-the-land techniques to bypass traditional security controls.
In February 2025, BlackBasta ransomware operations ceased after their internal chat logs were leaked online, leading to disbandment. However, former affiliates continued launching attacks using different ransomware families, including the relatively unknown Payouts King group that emerged in April 2025. ThreatLabz has observed continued ransomware activity consistent with former BlackBasta initial access brokers since early 2026, utilizing similar tactics including spam bombing, Microsoft Teams phishing, and Quick Assist abuse. Payouts King implements sophisticated evasion techniques including stack-based string obfuscation, API hashing, and direct system calls to terminate security processes. The ransomware leverages 4,096-bit RSA and 256-bit AES counter mode encryption, selectively encrypting files while targeting security software and employing anti-forensics techniques like shadow copy deletion and event log clearing.
A Microsoft Teams voice-phishing campaign leveraging Quick Assist, a remote administration tool, was tracked in September 2025. The campaign uses help desk scams to gain initial access, followed by user group enumeration and the execution of a PowerShell script to download a command and control payload. The attack employs AMSI bypass, encrypted communications, and a web-socket remote access trojan. Multiple Microsoft 365 tenants with IT-related subdomains were used, along with various IPs and domains for C2 infrastructure. The campaign shows similarities to Storm-1811 and PhantomCaptcha activities, suggesting a complex cybercrime ecosystem. The attackers' ultimate goal may be ransomware deployment, although observed attempts were successfully blocked.
The Chinese APT group Silver Fox has launched an SEO poisoning campaign targeting Chinese-speaking users, impersonating Microsoft Teams. The campaign uses a modified ValleyRAT loader with Cyrillic elements to mislead attribution. Silver Fox aims to conduct espionage and financial fraud, posing a significant threat due to its dual mission. The attack chain involves a fake Teams website, malicious ZIP files, and binary data retrieval from XML and JSON files. The malware exploits rundll32.exe for binary proxy execution and establishes C2 communication. Attribution to Silver Fox is based on overlapping infrastructure and links to previous campaigns. Organizations with global operations, especially in China, are advised to implement robust security measures and logging capabilities to defend against this evolving threat.
A sophisticated social engineering campaign exploits Microsoft Teams' 'Chat with Anyone' feature to impersonate IT support and trick users into initiating Quick Assist sessions. This multi-stage attack involves phishing, malware deployment (notably an infostealer named 'updater.exe'), and reconnaissance to steal credentials and potentially exfiltrate data. The threat actors leverage legitimate collaboration tools to bypass traditional security controls. Organizations are advised to disable the vulnerable Teams feature, enforce multi-factor authentication, and adopt Zero Trust principles to mitigate risks. No CVSS score is assigned, but the attack poses a medium severity risk due to its credential theft focus and social engineering complexity.
A new campaign is distributing the Oyster (Broomstick) backdoor through trojanized Microsoft Teams installers. Threat actors are using SEO poisoning and malvertising to trick users into downloading fake installers from spoofed websites. The malicious installers deploy a persistent backdoor that enables remote access, gathers system information, and supports additional payload delivery while evading detection. This tactic mirrors earlier fake PuTTY campaigns, showing a trend of abusing trusted software for initial access. The backdoor communicates with attacker-controlled C2 domains and uses DLL sideloading via rundll32.exe for stealthy execution. Organizations are advised to download software only from verified sources and avoid relying on search engine advertisements.
Matanbuchus 3.0, a malware loader available as Malware-as-a-Service, has evolved with significant updates. It now employs sophisticated techniques including improved communication protocols, in-memory stealth capabilities, enhanced obfuscation, and support for WQL queries, CMD, and PowerShell reverse shells. The loader collects detailed system data, including information on EDR security controls, to tailor subsequent attacks. It can execute various commands through regsvr32, rundll32, msiexec, or process hollowing. The malware establishes persistence through scheduled tasks and registry modifications. Recent campaigns have targeted victims through external Microsoft Teams calls impersonating IT helpdesks, leading to potential ransomware compromises.
