Quad7 Botnet Evolves to Target SOHO Routers and VPN Devices

The Quad7 botnet, a rapidly evolving threat, has expanded its attack surface to include SOHO (small office/home office) routers and VPN appliances from multiple manufacturers, aiming to compromise a wider range of devices by exploiting both known and unknown vulnerabilities.

Targeted Devices

    • Brands targeted include TP-Link, Zyxel, Asus, Axentra, D-Link, and NETGEAR. These devices are used in homes and small businesses, making them lucrative targets for attackers.
    • The botnet has been detected compromising devices across countries like Bulgaria, the U.S., and Ukraine.

Tactical Evolution

    • The botnet operators are upgrading their toolset, adding a new backdoor called UPDTAE to increase stealth capabilities. This backdoor allows remote control of infected devices via an HTTP-based reverse shell, enabling attackers to execute commands covertly.
    • Infected devices host two major services: one on TCP port 7777 (for communication with the command-and-control server) and another on port 11228, which hosts a SOCKS5 proxy server.

Multiple Botnet Clusters Identified

    • xlogin (7777 botnet): Compromised TP-Link routers with TCP ports 7777 and 11288 open.
    • alogin (63256 botnet): Targeting ASUS routers, opening TCP ports 63256 and 63260.
    • rlogin: Compromised Ruckus Wireless devices using TCP port 63210.
    • zylogin: Aimed at Zyxel VPN appliances using TCP port 3256.
    • axlogin: Capable of infecting Axentra NAS devices, though this hasn’t been detected in the wild yet.

State-Sponsored Threat

    • While the attackers’ full intentions remain unclear, new evidence points to the likelihood of the botnet being operated by Chinese state-sponsored threat actors, not just cybercriminals.
    • Brute-force attempts against Microsoft 365 and Azure instances have been observed, signaling broader cyber espionage activities.

Stealth and Evasion

    • Quad7 operators are deploying new malware variants on compromised devices to avoid detection and tracking by cybersecurity analysts, suggesting an ongoing effort to remain hidden while expanding their botnet infrastructure.

To protect your SOHO routers, VPN appliances, and other network devices from Quad7 and similar botnets:

  • Regularly update firmware on all network devices to patch vulnerabilities.
  • Disable unused ports and services to limit potential attack vectors.
  • Monitor traffic for unusual activity, especially on ports 7777, 11228, and other TCP ports linked to this botnet.

Stay vigilant, as cyber threats like the Quad7 botnet are becoming increasingly sophisticated, targeting critical network devices to evade detection.