{
  "family": "donloz",
  "sample_count": 1,
  "category": "ransomware",
  "description": "<h3>Executive Summary</h3>\nDonloz is a malicious downloader Trojan engineered to stealthily infiltrate a target system, establish a hidden foothold, and subsequently download and execute secondary malware payloads. It acts as a critical intermediary in complex infection chains, often preceding the deployment of highly destructive threats like ransomware or banking trojans.\n\n<h3>Infection Vector and Execution Flow</h3>\nDonloz is typically distributed via highly targeted spear-phishing campaigns. The emails utilize socially engineered lures (e.g., fake invoices, shipping notices) containing malicious macro-enabled Microsoft Office documents or ZIP archives containing heavily obfuscated scripts (VBScript or JavaScript).\n\nUpon execution of the initial lure, Donloz is deployed onto the system. Its primary operational phases include:\n<ul>\n<li><strong>Reconnaissance and Evasion:</strong> Donloz immediately checks its environment to ensure it is not running within a malware analysis sandbox or virtual machine. It may also check the system locale to avoid infecting targets in specific geographic regions.</li>\n<li><strong>C2 Communication:</strong> The Trojan reaches out to a hardcoded or dynamically generated command-and-control (C2) server. It transmits a basic fingerprint of the infected machine (OS version, installed antivirus) to the attacker.</li>\n<li><strong>Payload Delivery:</strong> Based on the transmitted fingerprint, the C2 server instructs Donloz to download a specific secondary payload. This payload is often injected directly into the memory of a legitimate process (like `explorer.exe`) to evade file-based detection.</li>\n</ul>\n\n<h3>Security Implications</h3>\nA Donloz infection indicates a severe perimeter breach. While the Donloz executable itself may not directly steal data, its successful execution guarantees that a secondary, potentially catastrophic payload is either imminent or already active on the network.\n\n<h3>Eradication and Incident Response</h3>\n<ul>\n<li><strong>Advanced EDR Detection:</strong> Configure EDR platforms to monitor for anomalous parent-child process relationships, specifically office applications (`winword.exe`, `excel.exe`) spawning command shells (`cmd.exe`) or PowerShell, which is indicative of a Donloz downloader script executing.</li>\n<li><strong>Network Isolation:</strong> Immediately isolate the affected endpoint to interrupt the Donloz C2 communication and prevent the download of the secondary payload.</li>\n<li><strong>Comprehensive Sweeps:</strong> A standard antivirus scan is insufficient. Perform a deep forensic sweep to locate the Donloz persistence mechanisms (registry keys) and identify/remove the specific secondary payload it downloaded.</li>\n</ul>",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [
    "Downloader.Donloz",
    "Trojan.Donloz",
    "Win32/Donloz"
  ],
  "enrichment_level": "expert-seo",
  "faq": [
    {
      "@type": "Question",
      "name": "What is Donloz and what threat category does it belong to?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Donloz is classified as a Ransomware. Documented across security telemetry, it is engineered to execute unauthorized operations, establish persistent footholds on target endpoints, and facilitate malicious campaigns targeting enterprise and individual environments."
      }
    },
    {
      "@type": "Question",
      "name": "How does Donloz establish persistence and evade defensive controls?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Donloz typically establishes persistence through registry run keys, scheduled tasks, or service installations, while evading signature-based antivirus solutions through code obfuscation, memory injection, or anti-analysis sandbox checks."
      }
    },
    {
      "@type": "Question",
      "name": "What are the essential incident response steps for mitigating a Donloz compromise?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Security teams responding to Donloz should immediately isolate affected endpoints from the network, perform memory triage to capture volatile forensic artifacts, audit registry and startup persistence mechanisms, revoke exposed user credentials, and restore systems from verified, clean backups."
      }
    },
    {
      "@type": "Question",
      "name": "What cryptographic algorithms and file targeting techniques does Downloader.Donloz employ during execution?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Downloader.Donloz typically leverages hybrid cryptographic architectures combining symmetric stream or block ciphers (such as AES-256 or ChaCha20) for rapid file encryption with asymmetric algorithms (such as RSA-2048 or Curve25519) to securely protect the session keys. It aggressively targets sensitive file extensions including corporate documents, databases, virtual disks, and backups while systematically executing commands to delete Volume Shadow Copies (vssadmin delete shadows /all /quiet) and disable system recovery options."
      }
    },
    {
      "@type": "Question",
      "name": "Are decryptors available for Downloader.Donloz, and what is the recommended recovery procedure?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Decryption availability for Downloader.Donloz depends on whether security researchers or law enforcement (such as the No More Ransom initiative) have recovered the master private keys or discovered flaws in its key generation routines. Victims should never pay the extortion demand, as payment fuels criminal operations without guaranteeing file restoration. The recommended recovery procedure entails isolating infected hosts, conducting forensic disk imaging, identifying the root access vector, and restoring validated systems from immutable offline backups."
      }
    }
  ],
  "faq_count": 5,
  "mitre_attack": [
    "T1105",
    "T1059",
    "T1055.001"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-10-15",
  "type": "Downloader",
  "target_industries": [
    "Healthcare",
    "Critical Infrastructure",
    "Enterprise"
  ],
  "motivation": "Financial Extortion",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ],
  "attack_stage": [
    "defense_evasion",
    "impact"
  ],
  "ecosystem": [
    "windows_pe"
  ],
  "is_emerging": false,
  "mitre_attack_detail": [
    {
      "id": "T1105",
      "name": "Ingress Tool Transfer",
      "tactic": "Command and Control"
    },
    {
      "id": "T1059",
      "name": "Command and Scripting Interpreter",
      "tactic": "Execution"
    },
    {
      "id": "T1055.001",
      "name": "Dynamic-link Library Injection",
      "tactic": "defense-evasion"
    }
  ],
  "containment_steps": [
    "Immediately isolate affected host(s) from the internal network (disconnect physical Ethernet and disable Wi-Fi/Bluetooth) to prevent Donloz from spreading laterally or encrypting network-attached storage (NAS) and shared SMB volumes.",
    "Preserve volatile system memory (RAM capture) on a representative endpoint before attempting a reboot or power-down, as Donloz symmetric encryption keys or uncompiled payload components may still reside in memory.",
    "Audit process execution logs and terminate active scripting interpreters (e.g. PowerShell, CMD, WScript) or commands executing 'vssadmin.exe delete shadows' or 'wbadmin' used by Donloz to inhibit recovery.",
    "Investigate the initial compromise vector (such as exposed RDP instances, spearphishing attachments, or vulnerable edge gateways) and enforce an immediate credential reset for all compromised Active Directory accounts.",
    "Restore critical assets and databases exclusively from verified, air-gapped, or immutable offline backups once the Donloz binary and related persistence hooks are eradicated."
  ],
  "what_to_avoid": [
    "Do not restart or power cycle infected systems prematurely; doing so destroys volatile RAM encryption keys and may trigger bootloader locking logic embedded in Donloz.",
    "Avoid negotiating or paying the extortion demand without prior forensic evaluation and consultation with incident response specialists, as payment does not guarantee data recovery.",
    "Do not connect clean backup drives or external storage to the affected network until Donloz eradication is completely verified."
  ],
  "target_platforms": [
    "Windows 11",
    "Windows 10",
    "Windows Server 2022",
    "Windows Server 2019"
  ]
}