The "Cavalry Werewolf" attack campaign is a recently identified high-priority cyber threat targeting Russian government agencies. This campaign employs two malware families named FoalShell and StallionRAT. FoalShell is likely a modular backdoor or loader used to establish initial foothold and persistence within compromised networks, while StallionRAT is a Remote Access Trojan designed to provide attackers with extensive control over infected systems. The campaign's technical details are sparse, with minimal public discussion and no known exploits in the wild reported yet. However, the use of RATs and backdoors in targeted attacks against government entities suggests a sophisticated threat actor aiming for espionage, data exfiltration, or disruption. The attack vector, infection chain, and specific vulnerabilities exploited remain undisclosed, but the targeting of Russian agencies implies a geopolitical motivation. The campaign was first reported on October 3, 2025, via a trusted cybersecurity news source, The Hacker News, and surfaced on Reddit's InfoSecNews subreddit, indicating early-stage public awareness. Given the malware types involved, the threat likely involves stealthy persistence mechanisms, command and control communications, and potential lateral movement within networks.

For European organizations, especially those with diplomatic, intelligence, or governmental ties to Russia or involved in Eastern European security matters, the "Cavalry Werewolf" campaign poses a significant risk. Although the campaign currently targets Russian agencies, the malware families FoalShell and StallionRAT could be repurposed or adapted to target European entities, particularly those engaged in geopolitical or intelligence operations related to Russia. The potential impacts include unauthorized access to sensitive information, espionage, disruption of critical government functions, and compromise of national security data. Additionally, supply chain risks exist if European contractors or partners of Russian agencies are targeted or compromised. The stealthy nature of RATs increases the risk of prolonged undetected presence, enabling extensive data theft or sabotage. The campaign's high severity rating underscores the need for vigilance in monitoring for similar tactics, techniques, and procedures (TTPs) within European networks.

European organizations should implement targeted detection and response measures focusing on RAT and backdoor behaviors. Specific recommendations include: 1) Deploy advanced endpoint detection and response (EDR) solutions capable of identifying FoalShell and StallionRAT signatures or behaviors, including unusual process injections, network beaconing, and persistence mechanisms. 2) Conduct threat hunting exercises using IoCs and behavioral indicators associated with these malware families, even if direct IoCs are not yet publicly available. 3) Harden network segmentation, particularly for sensitive government and intelligence systems, to limit lateral movement opportunities. 4) Enforce strict access controls and multi-factor authentication (MFA) to reduce the risk of credential theft and misuse. 5) Monitor network traffic for anomalous outbound connections to suspicious command and control servers, employing DNS and IP reputation filtering. 6) Maintain up-to-date threat intelligence feeds and collaborate with national cybersecurity centers to share information on emerging threats related to this campaign. 7) Train security teams to recognize early signs of RAT infections and conduct regular incident response drills simulating similar attack scenarios. 8) Review and update incident response plans to address espionage-focused campaigns with stealthy malware components.