{
  "family": "extcrome",
  "sample_count": 2,
  "category": "advanced_threat",
  "description": "Adware:Win32/Extcrome is an intrusive Potentially Unwanted Program (PUP) categorized as a malicious Browser Extension, specifically targeting Google Chrome. It forcibly alters a user's web browsing experience by manipulating browser settings, injecting unwanted advertisements into webpages, and tracking user browsing behavior to generate illicit Pay-Per-Click (PPC) revenue for its creators.<br><br><b>Understanding Extcrome</b><br>To an end-user, Extcrome manifests as a sudden influx of unremovable toolbars, persistent pop-up ads, 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 (malicious advertisements) (`T1189`).<br><br><b>Execution and Hijacking Mechanics</b><br>Extcrome is typically distributed via deceptive software bundles, fake software updates, or by tricking the user on malicious download portals. Upon execution, it modifies the Windows Registry (`T1112`) and browser configuration files (like Chrome's `Preferences` file) to force-install the extension (`T1176`). To ensure the hijacking cannot be easily reversed, it often installs a persistent scheduled task or Windows Service (`T1543.003`) acting as a 'watchdog'. This watchdog monitors the browser settings; if the user attempts to remove the extension or reset their homepage, the watchdog instantly re-installs Extcrome and reverts the settings back to the hijacked state.<br><br><b>Indicators of Compromise & Impact</b><br>The impact is a severely degraded user experience, potential privacy violations (tracking of search queries), and exposure to potentially malicious ads. Host-based IoCs include EDR alerts for modifications to browser shortcut properties, unexpected additions to Chrome's `Extensions` directory (`%LocalAppData%\\Google\\Chrome\\User Data\\Default\\Extensions`), or anomalous watchdog executables running from `%AppData%`. Network IoCs include DNS queries resolving to adware tracking infrastructure and redirected search traffic.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [
    {
      "@type": "Question",
      "name": "What is Extcrome and what threat category does it belong to?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Extcrome is classified as a Advanced Threat. 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 Extcrome establish persistence and evade defensive controls?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Extcrome 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 Extcrome compromise?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Security teams responding to Extcrome 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 lateral movement and credential access tactics does Extcrome leverage in enterprise intrusions?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Extcrome frequently utilizes privileged account harvesting techniques such as LSASS memory dumping, Kerberoasting, and token impersonation to escalate privileges. Once administrative credentials are acquired, it pivots across the victim network utilizing living-off-the-land binaries (LOLBins) such as WMI, PowerShell remoting, and PsExec, or abuses remote desktop protocols (RDP) to reach critical internal repositories and domain controllers."
      }
    },
    {
      "@type": "Question",
      "name": "How does Extcrome maintain covert communications and evade perimeter network monitoring?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Extcrome often relies on multi-stage command and control (C2) architectures utilizing encrypted protocols over standard web ports (HTTPS/443 or DNS tunneling) to blend in with legitimate enterprise network traffic. Many variants incorporate proxy networks, domain fronting, or cloud services (such as Microsoft Graph API, Google Drive, or Telegram) to masquerade C2 channels, bypassing traditional signature-based egress filtering."
      }
    }
  ],
  "faq_count": 5,
  "mitre_attack": [
    "T1562.001",
    "T1176",
    "T1112"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1176",
      "name": "Browser Extensions (Force-installing the malicious Chrome extension)",
      "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 and watchdog persistence)",
      "tactic": "Defense Evasion"
    }
  ],
  "containment_steps": [
    "Boot the infected machine into 'Safe Mode' to prevent the Extcrome watchdog process from loading and reverting your cleanup efforts.",
    "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 Chrome's AppData directory and reset the browser to default settings.",
    "Run a thorough scan with an enterprise-grade Adware/PUA removal tool to clean up deep registry persistence mechanisms."
  ],
  "what_to_avoid": [
    "Do not simply change the homepage back manually in Chrome; the persistent watchdog task will revert it on the next launch.",
    "Avoid allowing users to download software or browser extensions from unverified third-party portals."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ],
  "attack_stage": [
    "execution",
    "persistence"
  ],
  "ecosystem": [
    "windows_pe"
  ],
  "is_emerging": false,
  "target_platforms": [
    "Windows 11",
    "Windows 10",
    "Windows Server 2022",
    "Windows Server 2019"
  ]
}