FoalShell
FoalShell is a lightweight reverse shell used in campaigns attributed by BI.ZONE to the threat actor Cavalry Werewolf, which is assessed to overlap with YoroTrooper and several related clusters, with reported ties to Tomiris. It has been observed targeting the Russian public sector, including state agencies and organizations in the energy, mining, and manufacturing sectors. The malware has been delivered via targeted phishing emails observed between May and August 2025, where messages impersonated Kyrgyz government officials and distributed RAR archives that installed FoalShell or StallionRAT; in at least one case, a legitimate email account associated with a Kyrgyz regulatory authority was reportedly compromised and used for delivery. FoalShell is reported to exist in Go, C++, and C# variants and allows operators to execute arbitrary commands through cmd.exe. It was described alongside Telegram-based C2 activity in reporting on the campaign. Associated tooling in the broader intrusion set included ReverseSocks5Agent and ReverseSocks5 for reverse proxying. No specific FoalShell IOCs were provided in the content.
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Groups observed using it
2 distinct threat actors attributed by public researchers. Open in Mallory to see the full evidence chain and overlapping campaigns.
The latest phishing attacks, observed between May and August 2025, involve sending email messages using fake email addresses that impersonate Kyrgyzstan government employees to distribute RAR archives that deliver FoalShell or StallionRAT. ... FoalShell is a lightweight reverse shell that appears in Go, C++, and C# versions, allowing the operators to run arbitrary commands using cmd.exe.
"Cavalry Werewolf APT Targets Russian Agencies with FoalShell and Telegram C2"
Recent activity
3 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Named malware referenced as being used by the Cavalry Werewolf APT to target Russian agencies; described in the context of using Telegram as a command-and-control (C2) channel.
Custom reverse shell used in espionage campaigns attributed to the Cavalry Werewolf/YoroTrooper cluster.
A lightweight reverse shell (implemented in Go, C++, and C#) used to provide remote command execution on compromised hosts via cmd.exe.
The version that knows your environment.
Match every observed IP, domain, and hash against your live telemetry.
Named campaigns wielding this family, with evidence pinned to each claim.
CVEs this family uses for access and lateral movement.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Every documented technique, ranked by evidence weight.
Reddit, Mastodon, and CTI community discussion around this family.