Researchers from cybersecurity company Sekoia have conducted a significant operation by sinkholing a command and control server of a PlugX malware variant. Over six months, they observed more than 2.5 million connections from unique IP addresses worldwide, with daily requests from infected hosts exceeding 90,000. This extensive analysis revealed that the malware had affected systems across more than 170 countries, with a majority of infections concentrated in just 15 countries, including Nigeria, India, China, and the United States.
The operation began when Sekoia acquired the IP address of a dormant PlugX command and control server for only $7 and gained shell access by coordinating with the hosting provider. By setting up a simple web server to mimic the original command and control server’s behavior, the researchers were able to capture HTTP requests from infected hosts. This setup allowed them to monitor the malware’s spread and understand its operational mechanics, providing crucial insights into the flow and source of the infections.
The data collected from the sinkhole operation provides an intriguing glimpse into the victimology of the malware, suggesting a strategic interest from China as most infections were in countries involved in China’s Belt and Road Initiative. However, researchers caution that this conclusion should be considered carefully due to the widespread distribution of the malware after four years of activity. Originally tied to Chinese state-sponsored activities, PlugX has evolved into a commonly used tool by various threat actors for purposes ranging from espionage to financially motivated attacks.
To address the challenge of disinfecting infected systems, Sekoia has developed two main strategies. The first involves sending a self-delete command that PlugX supports, which can remove the malware without additional interventions. However, due to the wormable nature of PlugX, which allows it to spread via USB devices, a more comprehensive approach involves deploying a custom payload that can eradicate the malware from both the system and any connected USB drives. Despite these efforts, Sekoia acknowledges that air-gapped networks and unconnected USB drives infected with PlugX remain beyond reach for remediation.
