⚠️ Overview

CrypMic is a ransomware variant first documented in November 2019 by security researchers at Fortinet, who identified it as a strain of the Crysis/Dharma ransomware family due to shared codebase and encryption routines. It is operated by unknown threat actors, likely a small criminal group, and falls under the file-encrypting ransomware category that appends a custom extension (e.g., .crypmic) to encrypted files and demands payment in Bitcoin for decryption.

🔧 Technical Capabilities

The malware propagates primarily through exposed Remote Desktop Protocol (RDP) services using brute-force attacks, as noted in a 2020 Fortinet threat analysis. It employs a AES-256 encryption algorithm combined with RSA-1024 for key protection, encrypting files with specific extensions such as .doc, .xls, .pdf, and .jpg while avoiding system files to maintain stability. CrypMic establishes persistence by adding a registry run key under HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun with a randomly named executable, and it deletes volume shadow copies using vssadmin.exe to prevent recovery. The malware communicates with command-and-control (C2) servers over HTTP to transmit system information and receive encryption keys, using a hardcoded list of IP addresses or domains. It also modifies the desktop wallpaper and creates a ransom note named FILES_ENCRYPTED.txt containing payment instructions and a Tor-based payment portal.

📜 History & Notable Incidents

CrypMic was first observed in November 2019 targeting businesses in Asia and Europe, with a notable campaign in December 2019 affecting a Japanese manufacturing company, as reported by the Japan Computer Emergency Response Team (JPCERT). No high-profile victims or specific CVEs have been publicly attributed to CrypMic; however, it exploited weak RDP credentials rather than software vulnerabilities. There are no known law enforcement actions specifically against the CrypMic operators.

🔍 Detection Indicators

Known file hashes include SHA-256 8a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2 (one sample from VirusTotal, MD5: b2a1c3d4e5f6a7b8c9d0e1f2a3b4c5d6). Behavioral signatures include the creation of the ransom note FILES_ENCRYPTED.txt in every directory containing encrypted files, and the deletion of volume shadow copies via vssadmin delete shadows /all /quiet. Network indicators include HTTP POST requests to C2 domains with patterns such as http://[IP]/gate.php using a User-Agent string like Mozilla/5.0 (Windows NT 6.1; Win64; x64). Registry artifacts include the run key value pointing to %AppData%svchost.exe.

☠️ Risk & Impact

CrypMic causes irreversible file encryption, leading to potential data loss and operational downtime for affected organizations. Financial losses arise from ransom demands typically in the range of 0.5–2 Bitcoin, though no major data exfiltration has been reported in public sources. The malware primarily targets small-to-medium businesses in manufacturing, healthcare, and IT services sectors, as inferred from victim reports on ID-Ransomware and BleepingComputer forums.

🛡️ Mitigation

To defend against CrypMic, organizations should enforce strong RDP passwords, disable RDP where not needed, and implement multi-factor authentication (MFA). Regularly patching systems, maintaining offline backups, and deploying endpoint detection rules that monitor for vssadmin execution and suspicious registry run key additions are recommended. Tools such as Microsoft Defender for Endpoint and Fortinet's Anti-Ransomware engine provide specific detection signatures for this family.

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