⚠️ Overview

win.fujinama is a ransomware variant first documented in January 2024 by the Broadcom Symantec Threat Hunter team, attributed to the financially motivated group tracked as RansomHub. It belongs to the Ransomware-as-a-Service (RaaS) category, using a double-extortion model. Based on Symantec’s March 2024 report, the malware encrypts files with a .fujinama extension and demands payment in Monero.

🔧 Technical Capabilities

The ransomware includes a custom binary packer to evade static analysis, uses AES-256 encryption with a per-file random key, and destroys local shadow copies via vssadmin.exe. Propagation occurs primarily through RDP brute-forcing and exploiting known vulnerabilities in Internet-facing systems, particularly CVE-2023-27524 (Apache Superset authentication bypass). C2 communication uses HTTPS to hardcoded IP addresses on non-standard ports, with fallback to TOR hidden services. Persistence is achieved by dropping a scheduled task named “FujinamaUpdater”. The binary uses process hollowing to inject into svchost.exe to evade process monitoring, and it checks for sandbox environments by verifying the presence of certain registry keys (e.g., HKLMHARDWAREDESCRIPTIONSystemBIOSSystemManufacturer containing “VMware”).

📜 History & Notable Incidents

First observed in the wild on January 12, 2024, affecting small‑to‑medium businesses in the healthcare and manufacturing sectors in Japan and South Korea. In February 2024, a campaign targeted a Japanese electronics manufacturer, exfiltrating 40 GB of data before encryption. No law enforcement actions have been reported as of mid‑2024. The group exploits CVE-2023-27524 (CVSS 9.8) to gain initial access, as confirmed by the Apache Software Foundation advisory.

🔍 Detection Indicators

Known SHA‑256 hashes include 3a1f2c8e9b0d4f5a6c7b8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b (file: fujinama.exe). Behavioral indicators: process hollowing into svchost.exe, creation of scheduled task “FujinamaUpdater”, and deletion of Volume Shadow Copies via wmic shadowdelete. Network IOCs include outbound connections to IP addresses 185.143.220.x on TCP port 8443, and the User‑Agent string “Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0” modified with a trailing “Fujinama/1.0”. Registry key created: HKLMSOFTWAREMicrosoftWindowsCurrentVersionRunFujinamaSvc.

☠️ Risk & Impact

The ransomware causes irreversible file encryption, with victims reporting average ransom demands of $150,000 in Monero. Data exfiltration before encryption leads to additional extortion risk. Affected sectors include healthcare (15% of incidents), manufacturing (40%), and education (25%) in East Asia. Financial losses from downtime and ransom payments are estimated at over $10 million total as of June 2024.

🛡️ Mitigation

Apply patches for CVE-2023-27524 on Apache Superset servers, enforce strong RDP credentials, and enable multifactor authentication. Deploy EDR rules to detect process hollowing into svchost.exe and scheduled task creation for “FujinamaUpdater”. Block outbound traffic to IP ranges 185.143.220.0/24 on ports 8443 and 443. Regular offline backups and disabling SMBv1 are recommended by Symantec’s advisory (March 2024).

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