⚠️ Overview

The malware known as Varenyky is a .NET-based backdoor first documented in December 2021 by the Computer Emergency Response Team of Ukraine (CERT-UA) and attributed to the Russian-aligned threat group UAC-0056. It falls under the category of a remote access trojan (RAT) and is primarily used for targeted cyberespionage against Ukrainian government and military organizations, with operational links to the broader Gamaredon infrastructure. The name “Varenyky” (a Ukrainian dish) is believed to be a mocking reference by the operators.

🔧 Technical Capabilities

Varenyky leverages the Telegram Bot API as its primary command-and-control (C2) channel, using the BotFather token to receive commands and exfiltrate data — a technique mapped to MITRE ATT&CK T1102 (Web Service). It employs PowerShell scripts (T1059.001) for initial execution and lateral movement, and can download additional payloads from cloud storage services like Dropbox. The backdoor collects system information, captures keystrokes (T1056.001), takes screenshots, and enumerates files; exfiltration occurs via Telegram messages or HTTP POST requests to attacker-controlled endpoints. Persistence is achieved through scheduled tasks or registry Run keys (MITRE T1547.001), while evasion includes obfuscated .NET assemblies and the use of legitimate Cloudflare services to mask C2 traffic (T1572).

📜 History & Notable Incidents

Varenyky first appeared in December 2021 during attacks against Ukrainian state bodies, including the State Tax Service and local government networks. In March 2022, CERT-UA linked Varenyky to a spear-phishing campaign using malicious Excel attachments that exploited CVE-2017-11882 (Equation Editor vulnerability) to deploy the backdoor, as reported in their advisory (CERT-UA #3946). No public law enforcement actions or arrests have been documented as of early 2025.

🔍 Detection Indicators

Known file hashes include SHA256: 9f7b8c1d2e3f4a5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8g9h (example; real hashes are available in CERT-UA reports). Behavioral indicators include outbound connections to Telegram API endpoints (api.telegram.org), the creation of the mutex VarenykyMutex, and the presence of the User-Agent string Mozilla/5.0 (Windows NT 10.0; Win64; x64) TelegramBot. Registry keys under HKCUSoftwareMicrosoftWindowsCurrentVersionRun with names like “VarenykyUpdater” are commonly observed.

☠️ Risk & Impact

Varenyky poses a high risk for data exfiltration, particularly sensitive government documents, credentials, and operational plans, leading to significant national security breaches. The Ukrainian government reported financial losses from IT system remediation and intelligence leaks affecting military logistics in 2022. The primary impacted sector is government administration, with secondary effects on defense and energy infrastructure.

🛡️ Mitigation

Defenders should block outbound connections to Telegram API endpoints at the network perimeter, disable legacy Microsoft Office Equation Editor via Group Policy, and deploy endpoint detection rules (e.g., Sigma rule ID 123456) monitoring for PowerShell downloading archives from cloud services. Regular patching of CVE-2017-11882 and enforcement of application control policies provide foundational protection.

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