Rhombus is a Linux-based Distributed Denial of Service (DDoS) botnet that targets Virtual Private Servers (VPS) and Internet of Things (IoT) devices. The malware is designed to establish persistence on infected devices and includes a dropper component, which facilitates the installation of additional malicious payloads. The primary objective of Rhombus is to conscript compromised Linux systems into a botnet used for flooding attacks, overwhelming targeted networks or services with traffic to disrupt availability. The botnet's focus on VPS and IoT devices is significant because these systems often have varying levels of security and are frequently exposed to the internet, making them attractive targets for compromise. Persistence mechanisms enable Rhombus to maintain control over infected devices even after reboots or attempts to remove the malware, increasing the longevity and effectiveness of the botnet. While no specific vulnerabilities or exploits are detailed, the malware likely leverages weak or default credentials, unpatched services, or misconfigurations common in VPS and IoT environments to propagate. The absence of known exploits in the wild suggests that Rhombus may rely on opportunistic infection rather than targeted exploitation. The threat level is moderate (3 out of an unspecified scale), and the overall severity is classified as low by the source, reflecting limited immediate impact or sophistication compared to more advanced threats.

For European organizations, the Rhombus botnet poses a risk primarily through the compromise of VPS and IoT devices that are part of their infrastructure or supply chain. Infected devices can be used as launch points for DDoS attacks against critical services, potentially causing service outages and reputational damage. Additionally, the persistence and dropper capabilities mean that infected devices could be further exploited for other malicious activities, such as data exfiltration or lateral movement within networks. Organizations relying on IoT devices with limited security controls or VPS providers with inadequate hardening are particularly vulnerable. The impact is compounded by the potential for large-scale DDoS campaigns that could affect internet-facing services, cloud platforms, or critical infrastructure. However, since Rhombus does not appear to exploit zero-day vulnerabilities or advanced techniques, the threat is more opportunistic and manageable with proper security hygiene. The low severity rating indicates that while the threat should not be ignored, it is unlikely to cause catastrophic damage if appropriate mitigations are in place.

To mitigate the risk posed by Rhombus, European organizations should implement targeted security measures beyond generic advice: 1) Enforce strong, unique credentials on all VPS and IoT devices, avoiding default or weak passwords. 2) Regularly update and patch all devices, including IoT firmware and VPS operating systems, to close known vulnerabilities that could be exploited for initial compromise. 3) Employ network segmentation to isolate IoT devices and VPS instances from critical internal networks, limiting lateral movement opportunities. 4) Monitor network traffic for unusual outbound connections or traffic spikes indicative of DDoS activity originating from internal devices. 5) Utilize endpoint detection and response (EDR) solutions capable of identifying persistence mechanisms and dropper behaviors specific to Linux environments. 6) Implement strict access controls and disable unnecessary services on VPS and IoT devices to reduce the attack surface. 7) Collaborate with VPS providers to ensure security best practices are enforced and incident response capabilities are in place. 8) Conduct regular security audits and penetration testing focused on IoT and VPS infrastructure to identify and remediate weaknesses proactively.