The cybersecurity landscape is witnessing a significant evolution of the Quad7 botnet, as reported by Sekoia analysts. Initially known for targeting TP-Link and ASUS routers, Quad7 has now expanded its reach to include Zyxel VPN devices, Ruckus wireless routers, and Axentra media servers. This expansion marks a concerning development in the botnet’s capabilities and potential impact.
Quad7’s Expanding Arsenal and Targets
Quad7, named after its focus on port 7777, has demonstrated rapid growth and sophistication. The botnet now boasts new servers, clusters, backdoors, and reverse shells. Notably, it has shifted away from SOCKS proxies, opting for more covert operations. While the ultimate objectives of Quad7’s operators remain unclear, experts speculate that the botnet is being prepared for brute-force attacks on VPN, Telnet, SSH, and Microsoft 365 accounts.
Cluster Structure and Device Targeting
The botnet’s architecture consists of several clusters, each targeting specific devices and displaying unique banners when connecting to Telnet ports. For instance, Ruckus wireless devices show an “rlogin” banner. Some clusters, like “xlogin” and “alogin,” encompass thousands of compromised devices, while others, such as “rlogin” (active since June 2024) and “zylogin,” contain fewer infected units.
Advanced Evasion and Communication Techniques
Sekoia researchers have observed significant changes in Quad7’s attack methods and communication strategies. The malware now prioritizes detection evasion and operational efficiency. Key developments include:
- Abandonment of open SOCKS proxies: Previously used for malicious traffic during brute-force attacks.
- Adoption of KCP protocol: Enhances the botnet’s ability to avoid detection.
- Implementation of FsyNet tool: Utilizes UDP for data exchange, making threat tracking more challenging.
- Deployment of UPDTAE backdoor: Establishes HTTP reverse shells for remote control of infected devices without exposing login interfaces or open ports.
- Experimentation with “netd” binary: Employs the CJD route2 protocol for even more clandestine communications.
Implications for Cybersecurity
The evolution of Quad7 represents a significant threat to network security across various device types. Its advanced evasion techniques and expanded target range make detection and mitigation increasingly challenging. Organizations and individuals must remain vigilant, regularly update their devices, and implement robust security measures to protect against this evolving threat.
As Quad7 continues to develop, cybersecurity professionals must adapt their strategies to counter its sophisticated tactics. This includes enhancing network monitoring capabilities, implementing advanced intrusion detection systems, and educating users about the importance of strong, unique passwords and regular security updates. The cybersecurity community must remain proactive in sharing information and developing new defense mechanisms to stay ahead of this rapidly evolving botnet threat.
