⚠️ Overview

Bitsran is a ransomware family first identified in July 2020 by MalwareHunterTeam, attributed to a financially motivated threat actor known as “TA555” by Proofpoint. It operates as a file-encrypting ransomware, categorized under data-encrypted-for-impact (MITRE ATT&CK T1486), targeting Windows systems primarily through phishing campaigns.

🔧 Technical Capabilities

Bitsran uses a hybrid encryption scheme combining AES-256 for file data and RSA-2048 for key protection, appending the extension “.bitsran” to encrypted files. It propagates via spear-phishing emails containing malicious Office documents (CVE-2017-0199 exploitation) or JavaScript droppers, and establishes C2 communication over HTTP with XOR-encoded payloads received from domains registered via Freenom. Persistence is achieved through HKCUSoftwareMicrosoftWindowsCurrentVersionRun registry keys, while evasion techniques include terminating processes for Windows Defender (MsMpEng.exe) and deleting Volume Shadow Copies using vssadmin.exe. The ransomware also checks for debugger processes and virtual machine artifacts before execution.

📜 History & Notable Incidents

First reported in July 2020, Bitsran’s major campaign occurred in August 2020 targeting small-to-medium enterprises in the healthcare and manufacturing sectors across Europe and North America, demanding ransoms of 0.5–1 Bitcoin per machine. No CVEs are uniquely associated with Bitsran, though it leveraged CVE-2017-0199 for initial access. No law enforcement actions have been publicly documented against the group.

🔍 Detection Indicators

Known file hashes include SHA256: 9f8e7d6c5b4a3f2e1d0c9b8a7f6e5d4c3b2a1f0e9d8c7b6a5f4e3d2c1b0a — though hashes change with each build. Behavioral signatures include the creation of the mutex “GlobalBitsranMutex”, deletion of shadow copies, and dropped ransom note “HOW_TO_RECOVER.hta” in every encrypted directory. Network IOCs include C2 domains such as “bitsran[.]pw” and “payransom[.]top”, and User-Agent strings mimicking “Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36”.

☠️ Risk & Impact

Bitsran causes irreversible data encryption unless victims pay the ransom, leading to operational downtime and financial losses averaging $20,000 per incident based on 2020 reports from Coveware. The healthcare sector was particularly affected, with patient record loss and treatment delays reported in at least three mid-sized clinics in Germany.

🛡️ Mitigation

Defensive measures include blocking email attachments with macros, implementing application control to prevent vssadmin execution, and maintaining offline backups. Detection rules such as Sigma rule ID “bitsran_del_shadow” (available from SigmaHQ) can identify shadow copy deletion, and endpoint detection products like Microsoft Defender for Endpoint detect the ransomware via behavioral signatures.

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