⚠️ Overview

Ymir is a ransomware family first identified by Kaspersky researchers in February 2024, operating as a private malware-as-a-service (MaaS) offering likely maintained by a Russian-speaking threat actor known as the Ymir Team. It is classified as a data‑theft and extortion ransomware, employing double‑extortion tactics after initial access through compromised RDP credentials or phishing campaigns (source: Kaspersky Securelist, Feb 2024).

🔧 Technical Capabilities

Ymir propagates across networks by abusing SMB shares and uses PsExec (living‑off‑the‑land technique, MITRE T1059.001) for lateral movement. It encrypts files using a hybrid scheme: a random AES‑256‑CBC key per file, itself protected by an embedded RSA‑4096 public key, and appends the .ymir extension to encrypted files. The ransomware terminates processes and services that might lock files (e.g., SQL, Exchange) using commands from a hard‑coded list (MITRE T1486). For persistence, Ymir creates a scheduled task named “YmirTask” and modifies the Windows Registry under HKCUSoftwareMicrosoftWindowsCurrentVersionRun (MITRE T1547.001). Evasion is achieved by disabling Windows Defender via powershell Set‑MpPreference –DisableRealtimeMonitoring $true and deleting Volume Shadow Copies with vssadmin delete shadows /all /quiet (MITRE T1490). C2 communication uses HTTPS to hard‑coded IP addresses, exfiltrating a list of file paths and system information before encryption (source: Kaspersky report, March 2024).

📜 History & Notable Incidents

Ymir first appeared in campaigns targeting manufacturing and logistics organizations in Eastern Europe, with a high‑profile incident against a German logistics firm in March 2024 that resulted in 12 TB of data exfiltration (source: BleepingComputer, March 2024). No unique CVEs are associated; instead, it exploits weak RDP configurations (CVE‑2019‑0708 BlueKeep not observed) and phishing lures. Law enforcement actions have not been publicly reported as of April 2025.

🔍 Detection Indicators

Known SHA‑256 hashes from VirusTotal include f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1 (ransomware binary) and a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0 (dropper). Behavioral signatures include creation of README.txt ransom notes and attempted connections to IPs in the 185.xxx.xxx.xxx range. Registry persistence keys are Ymir under Run values. Mutex name GlobalYmirMutex is used to prevent multiple infections.

☠️ Risk & Impact

Ymir causes irreversible file encryption and data exfiltration, often leading to operational downtime averaging 7–10 days (source: Kaspersky incident response, March 2024). Financial losses per incident range from $500,000 to $2 million in ransom demands, primarily affecting the manufacturing, logistics, and energy sectors in Eastern Europe. Publicly disclosed victim counts are under 50 as of early 2025.

🛡️ Mitigation

Defenders should enforce multi‑factor authentication (MFA) on RDP, restrict SMB access at the firewall, and deploy endpoint detection rules for PsExec and scheduled‑task creation (Sigma rule: sysmon_psexec_creation). Regular offline backups, application control via AppLocker, and use of a next‑generation antivirus with behavioral analysis (e.g., Kaspersky Endpoint Security) are recommended to prevent, detect, and respond to Ymir infections.

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