{
  "family": "xunleihd",
  "sample_count": 2,
  "category": "advanced_threat",
  "description": "Adware:Win32/Xunleihd is an intrusive Potentially Unwanted Program (PUP) categorized as a malicious Browser Extension or Hijacker, primarily targeting users seeking media downloads or torrenting capabilities. It frequently piggybacks on or mimics the popular Chinese download manager 'Xunlei' (Thunder). It forcibly alters a user's web browsing experience by manipulating browser settings, injecting unwanted advertisements, and tracking user behavior to generate illicit Pay-Per-Click (PPC) revenue.<br><br><b>Understanding Xunleihd</b><br>To an end-user, Xunleihd manifests as an unexpected download manager toolbar, persistent pop-up ads offering HD video downloads, and the forced redirection of their default search engine to a low-quality, third-party portal. For a security team, it represents a breakdown in endpoint hygiene and a potential vector for more serious infections via malvertising (`T1189`).<br><br><b>Execution and Hijacking Mechanics</b><br>Xunleihd is typically distributed via deceptive software bundles, fake codec installers on streaming sites, or by tricking the user on malicious torrent portals. Upon execution, it modifies the Windows Registry (`T1112`) and browser configuration files to force-install the extension (`T1176`). It establishes persistence by creating a scheduled task or a run key to ensure the adware background processes (often named similarly to legitimate Xunlei processes to evade casual inspection) launch on boot. It then monitors network traffic to inject its own ads into HTTP streams and redirect search queries.<br><br><b>Indicators of Compromise & Impact</b><br>The impact is a severely degraded user experience, massive bandwidth consumption (if the P2P components are active), and exposure to potentially malicious ads. Host-based IoCs include EDR alerts for modifications to browser shortcut properties, unexpected additions to Chrome's or Firefox's Extensions directory, or anomalous executables running from `%AppData%` mimicking 'Thunder' or 'Xunlei' names if the legitimate software is not authorized. Network IoCs include DNS queries resolving to adware tracking infrastructure.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1562.001",
    "T1112",
    "T1176"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1176",
      "name": "Browser Extensions (Force-installing the adware component)",
      "tactic": "Persistence"
    },
    {
      "id": "T1112",
      "name": "Modify Registry (Changing default search/homepage keys)",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1562.001",
      "name": "Impair Defenses: Disable or Modify Tools (Browser hijacking)",
      "tactic": "Defense Evasion"
    }
  ],
  "containment_steps": [
    "Use the Windows Control Panel to uninstall the explicitly named adware program and the freeware application that originally bundled it.",
    "Manually remove the malicious extension folder from the browser's AppData directory and reset the browser to default settings.",
    "Audit the Windows Task Scheduler and remove any persistent tasks created by the adware.",
    "Run a thorough scan with an enterprise-grade Adware/PUA removal tool to clean up deep registry persistence mechanisms."
  ],
  "what_to_avoid": [
    "Do not assume the user intentionally installed the official Xunlei client; this adware often uses deceptive naming conventions.",
    "Avoid allowing users to download media players, codecs, or download managers from unverified third-party portals."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}