{
  "family": "extinstaller",
  "sample_count": 2,
  "category": "advanced_threat",
  "description": "Adware:Win32/Extinstaller is a classification for deceptive software components specifically designed to forcibly install unwanted, malicious, or ad-supported browser extensions into Chrome, Firefox, or Edge. It operates as a local privilege escalation and persistence mechanism, ensuring that even if a user deletes the extension from their browser, the local service will simply reinstall it (`T1189`).<br><br><b>Understanding Extinstaller (Browser Hijackers)</b><br>To an end-user, Extinstaller causes a highly frustrating browsing experience: homepages are changed, default search engines are hijacked, and web pages are injected with unwanted advertisements. For a security team, it represents a risk to corporate data, as these forced extensions often monitor all web traffic, capture search queries, and can potentially steal session cookies or credentials (`T1111`).<br><br><b>Execution and Persistence Mechanics</b><br>Extinstaller is typically bundled with freeware or pirated software. Upon execution, it does not rely on the browser's web store. Instead, it interacts directly with the browser's local configuration files or the Windows Registry. For Chrome, it often abuses the `ExtensionInstallForcelist` enterprise policy (`T1562.001`), locking the extension so the user cannot click 'Remove'. It establishes an OS-level persistence mechanism (a Scheduled Task or Registry Run key) (`T1547.001`) that constantly checks if the malicious extension is active and re-injects it if it has been removed.<br><br><b>Indicators of Compromise & Impact</b><br>The primary impact is privacy violation, browser hijacking, and exposure to malvertising. Host-based IoCs include unauthorized modifications to the `HKLM\\Software\\Policies\\Google\\Chrome\\ExtensionInstallForcelist` registry key, the presence of anomalous scheduled tasks running scripts or unknown executables, and the physical presence of unpacked extension files in `%LocalAppData%` outside the normal browser extension directories. Network IoCs involve constant background beaconing to advertising affiliate networks.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [
    {
      "@type": "Question",
      "name": "What is Extinstaller and what threat category does it belong to?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Extinstaller 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 Extinstaller establish persistence and evade defensive controls?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Extinstaller 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 Extinstaller compromise?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Security teams responding to Extinstaller 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 Extinstaller leverage in enterprise intrusions?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Extinstaller 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 Extinstaller maintain covert communications and evade perimeter network monitoring?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Extinstaller 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": [
    "T1189",
    "T1547.001",
    "T1562.001"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1562.001",
      "name": "Impair Defenses: Disable or Modify Tools (Abusing browser policies to prevent extension removal)",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1189",
      "name": "Drive-by Compromise (Initial distribution via software bundling)",
      "tactic": "Initial Access"
    },
    {
      "id": "T1547.001",
      "name": "Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder (Ensuring the reinstall service runs)",
      "tactic": "Persistence"
    }
  ],
  "containment_steps": [
    "Use an enterprise-grade Adware removal tool to locate and destroy the OS-level persistence mechanisms (the 'reinstaller' service).",
    "Manually remove the malicious registry keys enforcing the `ExtensionInstallForcelist` policy in Windows.",
    "Reset the affected web browsers to their default settings to clear out the malicious extension files and restore normal search behavior.",
    "Implement endpoint application control to prevent users from executing unvetted, bundled software installers."
  ],
  "what_to_avoid": [
    "Do not rely solely on removing the extension from within the browser's UI; Extinstaller is designed to defeat this action.",
    "Avoid ignoring adware infections in a corporate environment; malicious extensions can easily capture sensitive web application data."
  ],
  "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"
  ]
}