{
  "family": "liudoor",
  "sample_count": 1,
  "category": "ransomware",
  "description": "<h3>Executive Summary</h3>\nLiudoor is a malicious Backdoor Trojan designed to covertly infiltrate Windows systems, establish stealthy persistence, and provide a remote attacker with unfettered, unauthorized access to the compromised machine. Unlike simple downloaders, a backdoor allows the threat actor to directly interact with the system, execute arbitrary commands, and manually exfiltrate sensitive data.\n\n<h3>Infection Vector and Technical Capabilities</h3>\nLiudoor is typically distributed through targeted spear-phishing campaigns containing malicious attachments (often macro-enabled Office documents or weaponized PDFs) or by exploiting unpatched vulnerabilities in public-facing web servers or RDP (Remote Desktop Protocol) endpoints.\n\nOnce executed, Liudoor focuses on establishing a secure, persistent connection to the attacker:\n<ul>\n<li><strong>Command and Control (C2) Communication:</strong> The backdoor establishes a connection to a remote C2 server, often over encrypted channels (HTTPS) or via custom protocols on non-standard ports to evade Intrusion Detection Systems (IDS). It actively \"listens\" for incoming commands.</li>\n<li><strong>Remote Code Execution (RCE):</strong> The core functionality of Liudoor is to provide a remote shell. The attacker can execute arbitrary system commands (`cmd.exe` or PowerShell), upload or download files, and manipulate the Windows Registry at will.</li>\n<li><strong>Lateral Movement Facilitation:</strong> Because the attacker has interactive control, Liudoor is frequently used as a \"beachhead.\" The attacker will use the compromised host to scan the internal network, dump local credentials (using tools like Mimikatz), and pivot to more valuable servers or Domain Controllers.</li>\n</ul>\n\n<h3>Threat Assessment</h3>\nA Liudoor infection is a critical security incident. The presence of an active backdoor means the network perimeter has completely failed, and a human adversary currently has interactive access to the internal network. Data exfiltration or the deployment of enterprise-wide ransomware is often imminent.\n\n<h3>Incident Response and Remediation</h3>\n<ul>\n<li><strong>Immediate Isolation:</strong> The highest priority is to physically disconnect the infected machine from the network to sever the attacker's interactive connection and prevent further lateral movement. Do not power off the machine, as volatile memory (RAM) is required for forensic analysis.</li>\n<li><strong>Forensic Triage:</strong> Utilize Endpoint Detection and Response (EDR) or memory forensics to identify the specific processes associated with Liudoor, analyze its network connections to identify the C2 infrastructure, and determine if local administrator credentials have been dumped.</li>\n<li><strong>Enterprise Password Reset and Re-imaging:</strong> Because the attacker had interactive access, all credentials used on or accessible from the compromised endpoint must be reset immediately. The endpoint itself must undergo a complete bare-metal wipe and re-image from a trusted baseline.</li>\n</ul>",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [
    "Backdoor.Liudoor",
    "Trojan.Liudoor",
    "Win32/Liudoor"
  ],
  "enrichment_level": "expert-seo",
  "faq": [
    {
      "@type": "Question",
      "name": "What is Liudoor and what threat category does it belong to?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Liudoor 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 Liudoor establish persistence and evade defensive controls?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Liudoor 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 Liudoor compromise?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Security teams responding to Liudoor 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 Backdoor.Liudoor employ during execution?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Backdoor.Liudoor 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 Backdoor.Liudoor, and what is the recommended recovery procedure?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Decryption availability for Backdoor.Liudoor 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": [
    "T1059.003",
    "T1105",
    "T1573.001",
    "T1021"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-10-15",
  "type": "Backdoor / Trojan",
  "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": "T1059.003",
      "name": "Command and Scripting Interpreter: Windows Command Shell",
      "tactic": "Execution"
    },
    {
      "id": "T1105",
      "name": "Ingress Tool Transfer",
      "tactic": "Command and Control"
    },
    {
      "id": "T1573.001",
      "name": "Encrypted Channel: Symmetric Cryptography",
      "tactic": "Command and Control"
    },
    {
      "id": "T1021",
      "name": "Remote Services (Lateral movement to critical bank infrastructure)",
      "tactic": "Lateral Movement"
    }
  ],
  "containment_steps": [
    "Immediately isolate affected host(s) from the internal network (disconnect physical Ethernet and disable Wi-Fi/Bluetooth) to prevent Liudoor 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 Liudoor 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 Liudoor 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 Liudoor 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 Liudoor.",
    "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 Liudoor eradication is completely verified."
  ],
  "target_platforms": [
    "Windows 11",
    "Windows 10",
    "Windows Server 2022",
    "Windows Server 2019"
  ]
}