The Tsundere botnet, identified in mid-2025, represents an advanced malware campaign targeting Windows systems. It uniquely leverages the Ethereum blockchain to store and retrieve its command and control (C2) server addresses via smart contracts, which significantly enhances its resilience and evasion capabilities by decentralizing its infrastructure. The botnet operates using Node.js, allowing it to execute dynamic JavaScript code received from its C2 servers, enabling flexible and adaptive malicious operations. Infection vectors include MSI installers and PowerShell scripts, often disguised as popular games to entice users into executing them. Communications between infected hosts and C2 servers are encrypted using AES-256 in CBC mode, complicating network detection efforts. The botnet is linked to a Russian-speaking threat actor known as 'koneko' and is associated with the 123 Stealer malware, indicating a lineage of credential and data theft capabilities. Additionally, Tsundere features a marketplace and control panel that facilitate the creation, customization, and sale of bot variants, suggesting a commoditized malware-as-a-service model. The use of Ethereum smart contracts for C2 infrastructure is a novel technique that complicates takedown attempts by law enforcement and security teams, as blockchain data is immutable and globally distributed. The botnet employs multiple tactics and techniques mapped to MITRE ATT&CK, including obfuscation, credential access, persistence, and command execution. While no known exploits are currently reported in the wild, the botnet's capabilities and infrastructure indicate a significant emerging threat to Windows environments worldwide.

For European organizations, the Tsundere botnet poses substantial risks including unauthorized access to sensitive data, credential theft, and potential lateral movement within networks. The use of encrypted communications and dynamic code execution complicates detection and response efforts, increasing the likelihood of prolonged undetected presence. The decentralized C2 infrastructure via the Ethereum blockchain makes traditional takedown strategies ineffective, potentially allowing sustained operations. Organizations in sectors with high-value data or critical infrastructure could face data breaches, operational disruptions, and reputational damage. The botnet's distribution through gaming-related installers may particularly impact enterprises with employees or customers engaging in gaming activities, increasing infection vectors. Additionally, the commoditization of the botnet through its marketplace lowers the barrier for less skilled attackers to launch customized campaigns, potentially increasing attack volume and diversity. Overall, the threat could lead to increased incident response costs, regulatory scrutiny under GDPR for data breaches, and potential financial losses due to fraud or ransomware deployment by secondary actors leveraging the botnet.

1. Implement strict application whitelisting to prevent execution of unauthorized MSI installers and PowerShell scripts, especially those originating from untrusted sources or disguised as games. 2. Enforce PowerShell execution policies to restrict script execution and enable logging and monitoring of PowerShell activities to detect suspicious behavior. 3. Deploy endpoint detection and response (EDR) solutions capable of identifying Node.js-based malware and monitoring for dynamic JavaScript execution. 4. Monitor network traffic for unusual connections to Ethereum blockchain nodes or smart contract interactions, using threat intelligence to identify known malicious addresses. 5. Educate users about the risks of downloading and executing software from unverified sources, particularly gaming-related content. 6. Regularly update and patch Windows systems and security tools to reduce exploitation of known vulnerabilities. 7. Utilize threat hunting to identify indicators of compromise related to Tsundere, including encrypted communications and PowerShell/MSI execution patterns. 8. Collaborate with blockchain security experts to understand and monitor smart contract activities linked to the botnet. 9. Prepare incident response plans that consider the botnet's decentralized C2 infrastructure and encrypted communications to enable rapid containment and eradication.