{
  "family": "yiwanzhushou",
  "sample_count": 1,
  "category": "ransomware",
  "description": "<h3>Executive Summary</h3>\nYiwanzhushou is an aggressive Potentially Unwanted Program (PUP) and Adware application that operates primarily as a Browser Hijacker. It masquerades as a helpful browser extension, search optimizer, or coupon finder. Its true purpose is to forcefully inject advertisements, alter critical browser settings, and heavily monetize the infected endpoint through affiliate traffic generation and data harvesting.\n\n<h3>Infection Vector and Technical Capabilities</h3>\nYiwanzhushou relies almost entirely on deceptive software bundling. Users typically encounter it when downloading \"free\" software from unofficial, localized web portals or third-party aggregators. The adware is installed silently in the background during the primary software's setup process, often utilizing deceptive \"Advanced\" or \"Custom\" installation screens.\n\nOnce installed, the software employs highly aggressive tactics:\n<ul>\n<li><strong>Aggressive Browser Hijacking:</strong> The software installs persistent extensions across Chrome, Firefox, and Edge. It forcefully modifies the default homepage, search engine, and new tab page to route all traffic through affiliate-monetized search engines controlled by the adware developers.</li>\n<li><strong>System Watchdogs and Rootkit Tactics:</strong> Yiwanzhushou frequently installs background \"watchdog\" services that actively monitor the registry and browser settings. If a user attempts to remove the extension or change their homepage back to a legitimate search engine, the watchdog service instantly reinstalls the adware configurations.</li>\n<li><strong>Ad Injection and Overlay:</strong> It injects its own JavaScript into legitimate websites, overlaying pages with intrusive pop-up ads, sliding banners, and embedded video advertisements, significantly degrading system performance and user experience.</li>\n</ul>\n\n<h3>Threat Assessment</h3>\nWhile Yiwanzhushou is generally not classified as destructive malware (like ransomware), it poses a severe threat to system stability, user productivity, and privacy. The aggressive persistence mechanisms cause significant IT overhead, and the constant ad injection consumes massive CPU and RAM resources. The tracking telemetry also violates corporate privacy policies.\n\n<h3>Incident Response and Remediation</h3>\n<ul>\n<li><strong>Safe Mode and Process Termination:</strong> Due to the aggressive watchdog services, it is often necessary to boot the infected machine into Windows \"Safe Mode\" to prevent the adware's defense mechanisms from launching before attempting uninstallation.</li>\n<li><strong>Targeted Anti-Malware Scan:</strong> Standard antivirus often ignores PUPs. Utilize a reputable enterprise anti-malware solution (specifically tuned for Adware removal) to scan for and remove the deeply embedded registry keys and scheduled tasks.</li>\n<li><strong>Browser Factory Reset:</strong> Following the removal of the underlying files, a full factory reset of all installed web browsers is absolutely required to purge the malicious extensions and hijacked settings.</li>\n</ul>",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [
    "Adware.Yiwanzhushou",
    "PUP.Yiwanzhushou",
    "Win32/Adware.Hijacker"
  ],
  "enrichment_level": "expert-seo",
  "faq": [
    {
      "@type": "Question",
      "name": "What is Yiwanzhushou and what threat category does it belong to?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Yiwanzhushou 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 Yiwanzhushou establish persistence and evade defensive controls?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Yiwanzhushou 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 Yiwanzhushou compromise?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Security teams responding to Yiwanzhushou 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 Adware.Yiwanzhushou employ during execution?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Adware.Yiwanzhushou 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 Adware.Yiwanzhushou, and what is the recommended recovery procedure?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Decryption availability for Adware.Yiwanzhushou 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": [
    "T1185",
    "T1176",
    "T1546.015"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-10-15",
  "type": "Adware / Browser Hijacker",
  "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": "T1185",
      "name": "Browser Session Hijacking (Ad injection and tracking)",
      "tactic": "Collection"
    },
    {
      "id": "T1176",
      "name": "Browser Extensions",
      "tactic": "Persistence"
    },
    {
      "id": "T1546.015",
      "name": "Event Triggered Execution: Component Object Model Hijacking",
      "tactic": "Privilege Escalation"
    }
  ],
  "containment_steps": [
    "Immediately isolate affected host(s) from the internal network (disconnect physical Ethernet and disable Wi-Fi/Bluetooth) to prevent Yiwanzhushou 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 Yiwanzhushou 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 Yiwanzhushou 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 Yiwanzhushou 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 Yiwanzhushou.",
    "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 Yiwanzhushou eradication is completely verified."
  ],
  "target_platforms": [
    "Windows 11",
    "Windows 10",
    "Windows Server 2022",
    "Windows Server 2019"
  ]
}