APT31, also known by multiple aliases such as Altaire and Violet Typhoon, is a China-linked cyber espionage group active since at least 2010. Between 2024 and 2025, they targeted the Russian IT sector, focusing on companies that serve as contractors and integrators for government agencies. Their attacks are characterized by stealth and long-term undetected presence, leveraging legitimate cloud services like Yandex Cloud and Microsoft OneDrive for command-and-control (C2) and data exfiltration. This approach allows them to blend malicious traffic with normal network activity, complicating detection efforts. The group employs spear-phishing campaigns delivering payloads such as CloudyLoader via DLL side-loading, and uses encrypted commands hidden in social media profiles. Their toolset includes both custom and publicly available utilities for reconnaissance (SharpADUserIP), credential theft (SharpChrome.exe, Owawa IIS module), persistence (scheduled tasks mimicking legitimate apps), and tunneling (Tailscale VPN, Microsoft dev tunnels). They also use innovative C2 channels like Base64-encoded comments on VirusTotal and cloud storage services for covert communication. APT31’s objectives are intelligence gathering to benefit Beijing and state-owned enterprises politically, economically, and militarily. Their operational security includes timing attacks during weekends and holidays and maintaining server-mode tools awaiting attacker connections. The group’s activity overlaps with other clusters like EastWind, indicating possible shared infrastructure or tactics. Despite no known exploits in the wild for specific vulnerabilities, the group’s sophisticated use of cloud services and social engineering makes them a persistent threat. The medium severity rating reflects the moderate impact and complexity of exploitation, but the potential for significant espionage and data theft remains high.

For European organizations, especially those with business or governmental ties to Russia or operating in sectors targeted by APT31 (such as IT contractors, aerospace, defense, telecommunications, and government agencies), this threat poses a significant espionage risk. The use of legitimate cloud services for C2 and data exfiltration complicates detection and response, potentially allowing attackers to remain undetected for extended periods. Confidential data, including credentials, internal communications, and sensitive project information, could be compromised, undermining organizational integrity and trust. The stealthy nature of the attacks and the use of social media and cloud platforms for command channels increase the risk of lateral movement and supply chain compromises affecting European entities indirectly connected to Russian IT infrastructure. Additionally, the geopolitical context—heightened tensions involving China, Russia, and Europe—may increase the likelihood of spillover or targeting of European government and critical infrastructure sectors. The medium severity suggests a moderate but persistent threat that requires vigilant monitoring and tailored defenses.

European organizations should implement advanced network monitoring capable of detecting anomalous cloud service usage patterns, especially involving Yandex Cloud, Microsoft OneDrive, and other popular cloud platforms. Deploy behavioral analytics to identify unusual scheduled tasks mimicking legitimate applications and monitor for DLL side-loading activities. Enhance spear-phishing defenses by training users to recognize sophisticated email lures, including those with nested archives and shortcut files (LNK). Employ endpoint detection and response (EDR) solutions with capabilities to detect custom tools and backdoors like CloudyLoader and LocalPlugX variants. Restrict and audit the use of cloud storage and social media platforms for internal communications to reduce covert C2 channels. Use threat intelligence feeds to track APT31 indicators and update detection rules accordingly. Conduct regular security assessments of contractors and integrators, especially those interfacing with government agencies, to ensure supply chain security. Implement strict access controls and multi-factor authentication to limit credential theft impact. Finally, schedule incident response drills simulating stealthy, long-term intrusions to improve detection and remediation capabilities.