Cybercriminals are abusing Microsoft Teams as a gateway for their attacks. They then try to steal data or place ransomware. They also use email bombing and voice phishing. An initial analysis by Sophos X-Ops experts.
The active threat campaign investigated by Sophos X-Ops experts showed that two different groups of threat actors are infiltrating companies by abusing the functionality of the Office 365 platform and then attempting to extract data or plant ransomware. Particularly perfidious: the attackers use a combination of email bombing with up to 3.000 messages in less than an hour and subsequent voice or video calls via Teams, also known as voice phishing or vishing.
email bombing with up to 3.000 messages
After sending the first spam messages, the attackers pretend to be the technical support of the affected company, call via Teams and offer their "help" in solving the problem. When the employee answers the call and gives the criminals control of the computer using Quick Assist or Microsoft Teams screen sharing, the callers start rolling out the malware. As part of its investigation, Sophos X-Ops has uncovered links between the cybercriminals active in this campaign and the Russian threat groups Fin7 and Storm-1811.
The assessment of Sean Gallagher, Principal Threat Researcher at Sophos: "While the exploitation of remote management tools and the misuse of legitimate services in themselves is not entirely new, we are seeing an increasing number of threat groups using these tactics to target organizations of all sizes. This is an active threat campaign that we continue to monitor closely. Because the default configuration of Microsoft Teams allows anyone with a Teams account to chat or call employees within a company, many organizations are potentially vulnerable to this threat.
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disguise as a helpdesk manager
Additionally, many organizations use external providers for their IT support, so a call from an unfamiliar number labeled "Help Desk Manager" may not necessarily set off alarm bells. As Sophos continues to see new MDR and IR cases related to these tactics, we advise organizations using Microsoft 365 to be on high alert. They should review configurations and, where possible, block external account messages and remote access tools that are not regularly used."
More at Sophos.com
About Sophos
More than 100 million users in 150 countries trust Sophos. We offer the best protection against complex IT threats and data loss. Our comprehensive security solutions are easy to deploy, use and manage. They offer the lowest total cost of ownership in the industry. Sophos offers award-winning encryption solutions, security solutions for endpoints, networks, mobile devices, email and the web. In addition, there is support from SophosLabs, our worldwide network of our own analysis centers. The Sophos headquarters are in Boston, USA and Oxford, UK.
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