Security Company Arctic Wolf has reported that it has documented more than 400 incidents where threat actors flooded employees’ inboxes with spam, to the point of extreme frustration, then used Teams to contact the frustrated employee posting as IT support to assist in fixing the problem. The Teams contact comes within minutes of the flooding of the inbox. Because the Teams contact is from a legitimate platform and is not a vulnerability with Teams, the victim believes it is legitimate and accepts the help. This is another example of how threat actors use legitimate tools in a malicious way.
In using the legitimate Teams platform, the threat actor can bypass internal security measures to detect unauthorized activity, and legitimate IT professionals are unable to detect or defend users against the activity.
When the victim responds, Arctic Wolf found that it took the threat actor less than 15 minutes to obtain remote access. First, the threat actor asks the victim to switch to a Teams voice call and the threat actor then walks the victim through the installation of remote access software. The threat actor deploys the remote access software and starts running malicious code.
Be wary of any call or message from an outside organization, and only accept external chats with “specific partner domains.” IT professionals may wish to block “unmanaged Teams accounts and trial tenants and limiting Quick Assist and other remote access software to authorized IT staff.” Users should be aware of this threat and the unauthorized use of Teams, and to avoid any Teams chats or messages initiated from outside their organization. If your inbox gets flooded with spam, or you receive an unknown Teams call or chat, don’t answer it or respond–call your internal IT professionals on a reliable internal number.