Multiple distributed denial-of-service (DDoS) botnets are actively exploiting a critical vulnerability in Zyxel devices, which was discovered in April 2023.
The flaw, known as CVE-2023-28771, is a command injection bug affecting several firewall models and allows unauthorized actors to execute arbitrary code by sending a specially crafted packet to the targeted appliance.
Researchers from Fortinet FortiGuard Labs found that the attacks are taking place in various regions, including Central America, North America, East Asia, and South Asia. The vulnerability is being leveraged by multiple threat actors to compromise vulnerable systems and assemble a botnet capable of launching DDoS attacks against other targets.
The disclosure of the Zyxel vulnerability follows a warning from the Shadowserver Foundation about active exploitation since May 2023, indicating that the abuse of unpatched servers is on the rise. Fortinet’s latest findings reveal that the flaw is being opportunistically used by various botnets, including Mirai variants like Dark.IoT and a new botnet called Katana, which possesses DDoS capabilities using both TCP and UDP protocols. These botnets are employing multiple servers to launch attacks and are adapting quickly to maximize the compromise of Zyxel devices.
The increase in DDoS attacks has become more complex, with attackers employing novel methods to evade detection. Cloudflare reported a rise in sophisticated DDoS attacks in the second quarter of 2023, with threat actors mimicking browser behavior and utilizing DNS laundering attacks to conceal malicious traffic. DNS laundering involves querying subdomains of a victim’s managed domain, creating a large volume of requests that overwhelm the victim’s authoritative DNS server, disrupting legitimate queries, or even causing server crashes.
Additionally, pro-Russian hacktivist groups, such as KillNet, REvil, and Anonymous Sudan, have intensified their targeting of entities in the U.S. and Europe, aligned with Russian geopolitical priorities, presenting an additional cyber threat.
The evolving cyber threat landscape underscores the importance of proactive measures to protect against DDoS attacks and ensure the timely patching of known vulnerabilities in devices and systems.
Organizations should implement advanced monitoring, authentication, and authorization techniques while being vigilant against potential exploits by malicious actors. Addressing these vulnerabilities and adopting a zero trust architecture can help bolster the resilience of networks and protect against the growing threats posed by DDoS botnets.
