A newly tracked threat cluster identified as UNC6692 has been observed carrying out targeted intrusions by abusing Microsoft Teams, relying heavily on social engineering to deliver a sophisticated and multi-stage malware framework.
According to findings from Mandiant, the attackers impersonate internal IT help desk personnel and persuade employees to accept chat requests originating from accounts outside their organization. This method allows them to bypass traditional email-based phishing defenses by exploiting trust in workplace collaboration tools.
The attack typically begins with a deliberate email bombing campaign, where the victim’s inbox is flooded with large volumes of spam messages. This is designed to create confusion and urgency. Shortly after, the attacker initiates contact through Microsoft Teams, posing as technical support and offering assistance to resolve the email issue.
This combined tactic of inbox flooding followed by help desk impersonation is not entirely new. It has previously been linked to affiliates of the Black Basta ransomware group. Although that group ceased operations, the continued use of this playbook demonstrates how effective intrusion techniques often persist beyond the lifespan of the original actors.
Separate research published by ReliaQuest shows that these campaigns are increasingly focused on senior personnel. Between March 1 and April 1, 2026, 77% of observed incidents targeted executives and high-level employees, a notable increase from 59% earlier in the year. In some cases, attackers initiated multiple chat attempts within seconds, intensifying pressure on the victim to respond.
In many similar attacks, victims are convinced to install legitimate remote monitoring and management tools such as Quick Assist or Supremo Remote Desktop, which are then misused to gain direct system control. However, UNC6692 introduces a variation in execution.
Instead of deploying remote access software immediately, the attackers send a phishing link through Teams. The message claims that the link will install a patch to fix the email flooding problem. When clicked, the link directs the victim to download an AutoHotkey script hosted on an attacker-controlled Amazon S3 bucket. The phishing interface is presented as a tool named “Mailbox Repair and Sync Utility v2.1.5,” making it appear legitimate.
Once executed, the script performs initial reconnaissance to gather system information. It then installs a malicious browser extension called SNOWBELT on Microsoft Edge. This is achieved by launching the browser in headless mode and using command-line parameters to load the extension without user visibility.
To reduce the risk of detection, the attackers use a filtering mechanism known as a gatekeeper script. This ensures that only intended victims receive the full payload, helping evade automated security analysis environments. The script also verifies whether the victim is using Microsoft Edge. If not, the phishing page displays a persistent warning overlay, guiding the user to switch browsers.
After installation, SNOWBELT enables the download of additional malicious components, including SNOWGLAZE, SNOWBASIN, further AutoHotkey scripts, and a compressed archive containing a portable Python runtime with required libraries.
The phishing page also includes a fake configuration panel with a “Health Check” option. When users interact with it, they are prompted to enter their mailbox credentials under the assumption of authentication. In reality, this information is captured and transmitted to another attacker-controlled S3 storage location.
The SNOW malware framework operates as a coordinated system. SNOWBELT functions as a JavaScript-based backdoor that receives instructions from the attacker and forwards them for execution. SNOWGLAZE acts as a tunneling component written in Python, establishing a secure WebSocket connection between the compromised machine and the attacker’s command-and-control infrastructure. SNOWBASIN provides persistent remote access, allowing command execution through system shells, capturing screenshots, transferring files, and even removing itself when needed. It operates by running a local HTTP server on ports 8000, 8001, or 8002.
Once inside the network, the attackers expand their control through a series of post-exploitation activities. They scan for commonly used network ports such as 135, 445, and 3389 to identify opportunities for lateral movement. Using the SNOWGLAZE tunnel, they establish remote sessions through tools like PsExec and Remote Desktop.
Privilege escalation is achieved by extracting sensitive credential data from the system’s LSASS process, a critical Windows component responsible for storing authentication information. Attackers then use the Pass-the-Hash technique, which allows them to authenticate across systems using stolen password hashes without needing the actual passwords.
To extract valuable data, they deploy tools such as FTK Imager to capture sensitive files, including Active Directory databases. These files are staged locally before being exfiltrated using file transfer utilities like LimeWire.
Mandiant researchers note that this campaign reflects an evolution in attack strategy by combining social engineering, custom malware, and browser-based persistence mechanisms. A key element is the abuse of trusted cloud platforms for hosting malicious payloads and managing command-and-control operations. Because these services are widely used and trusted, malicious traffic can blend in with legitimate activity, making detection more difficult.
A related campaign reported by Cato Networks underlines similar tactics, where attackers use voice-based phishing within Teams to guide victims into executing a PowerShell script that deploys a WebSocket-based backdoor known as PhantomBackdoor.
Security experts emphasize that collaboration platforms must now be treated as primary attack surfaces. Controls such as verifying help desk communications, restricting external access, limiting screen sharing, and securing PowerShell execution are becoming essential defenses.
Microsoft has also warned that attackers are exploiting cross-organization communication within Teams to establish remote access using legitimate support tools. After initial compromise, they conduct reconnaissance, deploy additional payloads, and establish encrypted connections to their infrastructure.
To maintain persistence, attackers may deploy fallback remote management tools such as Level RMM. Data exfiltration is often carried out using synchronization tools like Rclone. They may also use built-in administrative protocols such as Windows Remote Management to move laterally toward high-value systems, including domain controllers.
These intrusion chains rely heavily on legitimate software and standard administrative processes, allowing attackers to remain hidden within normal enterprise activity across multiple stages of the attack lifecycle.
A contemporary cyber campaign has been identified where attackers are using Microsoft Teams to target employees in financial and healthcare organizations, eventually infecting systems with a newly observed malware known as A0Backdoor.
Research from BlueVoyant shows that the attackers rely heavily on social engineering. They begin by overwhelming an employee’s inbox with large volumes of spam emails. Soon after, they contact the same individual on Microsoft Teams, pretending to be part of the company’s IT support team and offering help to resolve the issue. This sequence is designed to build trust and make the request appear routine.
Once the victim is convinced, the attacker asks them to start a remote session using Quick Assist, a built-in Windows feature meant for remote troubleshooting. After access is granted, the attacker delivers a set of malicious tools through MSI installer files. These installers are digitally signed and hosted on a personal Microsoft cloud storage account, which helps them appear legitimate at first glance.
The researchers found that these MSI files are disguised as familiar Microsoft-related components, including Microsoft Teams elements and CrossDeviceService, a real Windows service used by the Phone Link application. This naming strategy helps the files blend in with normal system processes.
To execute the attack, the threat actor uses a technique called DLL sideloading. This involves running trusted Microsoft programs to load a malicious file named hostfxr.dll. Inside this file is data that is either compressed or encrypted. When the file is loaded into memory, it decrypts this data into shellcode and begins execution.
The malware also uses the CreateThread function to generate multiple threads. This behavior is not meant to improve performance but to make analysis harder. According to the researchers, creating too many threads can cause debugging tools to crash, even though it does not noticeably affect normal system activity.
After execution begins, the shellcode checks whether it is running inside a sandbox environment, which is commonly used by security analysts. If no such environment is detected, it proceeds to create a cryptographic key derived from SHA-256. This key is then used to decrypt the A0Backdoor payload, which is protected using AES encryption.
Once decrypted, the malware moves itself to a different region in memory and activates its main functions. It collects system-level information using Windows API calls such as DeviceIoControl, GetUserNameExW, and GetComputerNameW. This allows it to identify and profile the infected machine.
For communication with its operators, the malware avoids traditional methods and instead uses DNS traffic. It sends DNS MX queries that contain encoded data within complex subdomains to public recursive DNS servers. The responses it receives include MX records that carry encoded instructions. The malware extracts the relevant part of the response, decodes it, and then follows the commands.
Researchers explain that using MX records helps the traffic appear normal, making it harder to detect compared to other DNS-based techniques, especially those that rely on TXT records, which are more commonly monitored.
The campaign has already targeted at least two organizations, including a financial institution in Canada and a global healthcare company.
BlueVoyant assesses with moderate to high confidence that this activity builds on methods previously linked to the BlackBasta group. Although that group reportedly shut down after internal chat logs were leaked, parts of its approach appear to be continuing in this operation.
At the same time, the researchers point out that several elements in this campaign are new. These include the use of signed MSI installers, the A0Backdoor malware itself, and the use of DNS MX records for command-and-control communication.
This case reflects how attackers are adapting their methods by combining trusted tools, familiar platforms, and layered techniques to bypass detection.
Cybercriminals are increasingly targeting Microsoft Teams, utilizing the platform for sophisticated phishing, vishing, and ransomware campaigns. Exploiting Teams' widespread use, attackers employ social engineering tactics to deceive users and extract sensitive data. Methods range from fake job offers to malicious file sharing, aiming to infiltrate accounts and compromise organizational networks.
One notable tactic involves bypassing multifactor authentication (MFA). Threat actors, reportedly linked to the SolarWinds attack, create fraudulent “onmicrosoft.com” subdomains designed to mimic legitimate security entities. They send chat requests via Microsoft Teams, prompting users to enter a code into the Microsoft Authenticator app. This action grants attackers unauthorized access to Microsoft 365 accounts, enabling data theft or the integration of malicious devices into corporate networks.
The Black Basta ransomware group employs a different strategy by overwhelming users with spam emails and impersonating IT support staff on Teams. Claiming to assist with email issues, they persuade victims to install remote desktop tools, providing attackers with direct access to deploy malware. This includes Trojans and ransomware designed to exfiltrate sensitive data and compromise systems.
Another prevalent scheme involves fake job offers. Scammers contact individuals with fabricated employment opportunities, sometimes conducting entire interviews via Microsoft Teams chat. These scams often escalate to requests for personal information, such as Social Security numbers or tax details. In some cases, victims are asked to pay for materials or services, resulting in financial loss and potential identity theft.
Attackers also impersonate HR personnel, sending phishing messages about urgent policy updates. These messages frequently include malicious files disguised as legitimate updates. Once downloaded, malware like DarkGate is installed, granting attackers control over the victim’s system and network.
Additionally, compromised Microsoft 365 accounts are used to distribute malicious files through Teams chats. These files often appear as PDFs with double extensions, deceiving users into downloading executable malware. Once activated, these programs can breach data and facilitate deeper network infiltration.
Vigilance is essential in countering these threats. Users should verify unexpected messages, invitations, or file-sharing requests, especially those containing links or urgent calls to action. Tools that check link safety and domain age can help detect phishing attempts.
Organizations should prioritize employee education on recognizing scams and enforcing robust cybersecurity protocols. By staying informed and cautious, users can mitigate risks and safeguard against cyberattacks targeting Microsoft Teams.