MuddyWater APT Unveils ‘RustyWater’: A New Rust-Based Malware Menace

The cybersecurity landscape is constantly evolving, with advanced persistent threat (APT) groups continually refining their tactics to breach defenses. A prime example of this ongoing arms race is the recent activity from the Iran-linked MuddyWater APT group. Our analysis reveals a significant shift in their arsenal: a sophisticated spear-phishing campaign leveraging weaponized Word documents to deploy a novel Rust-based malware toolkit dubbed ‘RustyWater.’ This development marks a distinct departure from their historical reliance on PowerShell and VBS scripts, posing new challenges for traditional antivirus (AV) and endpoint detection and response (EDR) solutions.

MuddyWater’s Evolving Threat Landscape

MuddyWater, also known by aliases such as Static Kitten, Seedworm, and Mercury, has long been a formidable adversary, primarily targeting government agencies, telecommunications providers, and critical infrastructure organizations across the Middle East. Their operational methodology typically involves spear-phishing tailored to specific targets, followed by the deployment of custom backdoors and reconnaissance tools. The current campaign, however, demonstrates an elevated level of sophistication and a strategic re-tooling.

Targeted Sectors and Modus Operandi

This latest campaign targets high-value entities within diplomatic, maritime, financial, and telecommunications sectors throughout the Middle East. The initial infection vector remains consistent with MuddyWater’s playbook: meticulously crafted spear-phishing emails. These emails carry weaponized Microsoft Word documents. When opened and macros are enabled (a common social engineering trick employed by many APTs), these documents initiate the multi-stage infection process.

Introducing ‘RustyWater’: The Rust-Based Challenge

The most notable aspect of this campaign is the introduction of ‘RustyWater,’ a malware toolkit developed in the Rust programming language. This represents a significant strategic pivot for MuddyWater. Historically, the group has heavily utilized PowerShell and VBS for their implants, relying on the ubiquity and accessibility of these scripting languages within Windows environments. The adoption of Rust offers several advantages for the threat actors:

• Enhanced Evasion Capabilities: Rust’s compile-to-native code nature and its strong type safety can make it more challenging for signature-based AV and heuristic EDR solutions to detect, especially when compared to script-based malware.
• Cross-Platform Potential: While currently observed on Windows, Rust’s inherent cross-platform compilation capabilities might signal future intentions to target other operating systems.
• Performance and Reliability: Rust is known for its performance and memory safety, which can lead to more stable and efficient malware execution.
• Reduced Forensics Footprint: Native binaries can sometimes offer a smaller and less verbose forensic footprint compared to scripts that rely on a runtime environment.

The Shift from PowerShell and VBS Tooling

MuddyWater’s prior usage of PowerShell and VBS allowed for rapid development and deployment, leveraging living-off-the-land techniques. However, security vendors have invested heavily in detecting and mitigating threats that rely on these scripting languages. The move to Rust indicates MuddyWater’s ongoing adaptation to these enhanced defenses, seeking new avenues for persistent access and data exfiltration.

Remediation Actions and Proactive Defense

Defending against evolving threats like ‘RustyWater’ requires a multi-layered approach that combines technical controls with robust security awareness training. Organizations in the targeted sectors, and indeed all organizations, should take the following remediation actions:

• Strengthen Email Security: Implement advanced email filtering solutions capable of detecting and blocking malicious attachments and spear-phishing attempts. Utilise DMARC, DKIM, and SPF to prevent email spoofing.
• Disable Unnecessary Macros: Configure Microsoft Office applications to disable macros by default or to prompt users before enabling them. Educate users on the dangers of enabling macros from untrusted sources.
• Endpoint Detection and Response (EDR): Deploy and continuously monitor EDR solutions. Ensure EDR agents are up-to-date and configured to detect unusual process execution, file modifications, and network activity, even from novel binaries.
• Security Awareness Training: Conduct regular and engaging training sessions for all employees on identifying and reporting phishing attempts, particularly those disguised as legitimate documents. Emphasize the risks associated with enabling macros.
• Network Segmentation: Implement network segmentation to limit the lateral movement of threats within your environment should a breach occur.
• Regular Backups: Maintain comprehensive and regularly tested backup and recovery procedures to minimize the impact of successful attacks.
• Threat Intelligence Feeds: Subscribe to and integrate reliable threat intelligence feeds that provide indicators of compromise (IoCs) related to MuddyWater and other relevant APTs.

The Constant Evolution of Cyber Warfare

The emergence of ‘RustyWater’ serves as a stark reminder that cyber adversaries are constantly innovating. MuddyWater’s adoption of Rust signifies a willingness to invest in new development frameworks to bypass existing security controls. Organizations must remain vigilant, continually updating their defense strategies and fostering a culture of cybersecurity awareness to effectively counter these persistent and sophisticated threats.