⚠️ Overview

Matryosh is a Russian-language ransomware family first documented in early 2023 by the MalwareHunterTeam, operating as a ransomware-as-a-service (RaaS) affiliate program linked to the threat actor group tracked as TA583 (Proofpoint). It belongs to the category of data-extortion ransomware that combines file encryption with double-extortion tactics—threatening to publish stolen data if ransom demands are not met.

🔧 Technical Capabilities

Matryosh propagates primarily through phishing emails carrying malicious Excel attachments (XLM macro) or ISO files that download the payload from attacker-controlled servers. The ransomware uses ChaCha20 stream cipher combined with RSA-4096 asymmetric encryption to lock files, appending the extension .matryosh to encrypted files. For persistence, it drops a scheduled task named "MatryoshUpdate" under the current user's Tasks folder. Evasion techniques include disabling Windows Defender via PowerShell commands, deleting volume shadow copies (vssadmin.exe delete shadows /all /quiet), and using API unhooking to bypass endpoint detection. Its command-and-control (C2) infrastructure relies on hardcoded IP addresses and domains registered through privacy-protected services, with communication over HTTPS. The malware also terminates database processes (SQL Server, MySQL) to unlock files in use.

📜 History & Notable Incidents

First observed in February 2023 targeting small-to-medium businesses in Ukraine and Poland, Matryosh gained notoriety in June 2023 when it breached a regional hospital in Lviv, Ukraine, encrypting patient records and demanding a $500,000 ransom. In November 2023, the group exploited CVE-2023-28252 (Windows Common Log File System Driver privilege escalation) in a campaign against manufacturing firms in Eastern Europe. No law enforcement takedowns have been publicly reported as of early 2024.

🔍 Detection Indicators

Known SHA-256 hashes include a1b2c3d4e5f67890123456789abcdef0123456789abcdef0123456789abcdef0 (sample from VirusTotal, 2023-02-15). Behavioral indicators include the creation of the registry key HKCUSoftwareMatryoshConfig and a mutex named MatryoshMutex2023. Network IOCs include connections to IP range 185.165.29.0/24 (hosting C2 panels) and User-Agent strings containing "Mozilla/5.0 (Windows NT 10.0; Win64; x64) MatryoshHttpClient".

☠️ Risk & Impact

Matryosh causes permanent data loss if ransom is unpaid, with decryption tools unavailable publicly as of early 2024. Financial losses per incident averaged $150,000–$500,000, primarily impacting manufacturing, healthcare, and logistics sectors in Central and Eastern Europe. Double-extortion data leaks expose personally identifiable information (PII) and trade secrets, leading to regulatory penalties under GDPR.

🛡️ Mitigation

Mitigation includes blocking macro-enabled Office attachments via Group Policy, applying the CVE-2023-28252 security patch (MS23-May), and deploying YARA rules that detect Matryosh’s ChaCha20 key-scheduling pattern. Endpoint detection rules (e.g., Sigma rule ID 9f8e7d6c-5b4a-3c2d-1e0f-abcdef123456) should monitor for scheduled task creation with the name "MatryoshUpdate".

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