VPNFilter — a multi-stage, modular framework that has infected hundreds of thousands of network devices across the globe — is now known to possess even greater capabilities. Cisco Talos recently discovered seven additional third-stage VPNFilter modules that add significant functionality to the malware, including an expanded ability to exploit endpoint devices from footholds on compromised network devices. The new functions also include data filtering and multiple encrypted tunneling capabilities to mask command and control (C2) and data exfiltration traffic. And while we believe our work, and the work of our international coalition of partners, has mostly neutralized the threat from VPNFilter, it can still be difficult to detect in the wild if any devices remain unpatched.

Talos has been researching VPNFilter for months. Our initial findings are outlined here, and a description of additional modules used by the framework is here. As part of our continued investigation, we developed a technique to examine a key protocol used by MikroTik networking devices to hunt for possible exploitation methods used by the actor.

As we followed the thread of VPNFilter infections, it became clear that MikroTik network devices were heavily targeted by the threat actor, especially in Ukraine. Since these devices seemed to be critical to the actor’s operational goals, this led us to try to understand how they were being exploited. Part of our investigation included the study of the protocol used by MikroTik’s Winbox administration utility. In this blog, we’ll share how and why we studied this protocol, as well as the decoder tool we developed as a way of helping the security community look into this protocol for potential malicious actor activity.

The sophistication of VPNFilter drives home the point that this is a framework that all individuals and organizations should be tracking. Only an advanced and organized defense can combat these kinds of threats, and at the scale that VPNFilter is at, we cannot afford to overlook these new discoveries.



Talos Group

Talos Security Intelligence & Research Group