{
  "family": "vosteran",
  "sample_count": 8,
  "category": "advanced_threat",
  "description": "BrowserModifier:Win32/Vosteran is a highly persistent Potentially Unwanted Program (PUA) and browser hijacker that forcefully takes control of the user's web browsers. It replaces the default homepage, new tab page, and search engine with `vosteran.com` (or similar affiliate domains). Its primary goal is to drive massive amounts of forced web traffic to monetized search portals, generating illicit pay-per-click revenue for its operators.<br><br><b>Understanding Vosteran Hijackers</b><br>To an end-user, a Vosteran infection is a severely frustrating experience. Their browser is completely locked; attempts to manually change the settings back to Google or Bing are immediately reversed. For security analysts, Vosteran represents a complex adware framework. Unlike simple extensions, Vosteran utilizes deep operating system hooks, registry modifications, and watchdog services to ensure its persistence, making standard removal methods ineffective.<br><br><b>Execution and Hijacking Mechanics</b><br>Vosteran is primarily distributed via aggressive software bundlers (`T1189`) found on dubious freeware download sites. The installer uses deceptive pre-checked boxes to gain 'consent' (`T1204.002`). Upon execution, it installs malicious Browser Helper Objects (BHOs) (`T1176`) and forcefully alters the shortcut properties (`.lnk` files) of Chrome, Firefox, and Edge on the desktop and taskbar, appending the Vosteran URL as a command-line argument (`T1547.009`). Furthermore, it modifies the Windows Registry (`T1112`) to lock the browser settings and installs a background Windows Service (`T1543.003`) that acts as a watchdog. If the user manages to delete the extension or fix the shortcut, this watchdog service will instantly reinstall Vosteran.<br><br><b>Indicators of Compromise & Impact</b><br>The primary impact is a degraded user experience, forced redirection through potentially insecure ad networks, and a massive influx of helpdesk tickets. Incident responders will observe modified browser shortcuts (`chrome.exe http://vosteran.com...`). EDR logs will flag the installation of the Vosteran watchdog service and the unauthorized modification of browser registry keys (`HKLM\\SOFTWARE\\Policies\\Google\\Chrome`).",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1189",
    "T1543.003",
    "T1547.009",
    "T1176"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1189",
      "name": "Drive-by Compromise (Bundled Installers)",
      "tactic": "Initial Access"
    },
    {
      "id": "T1547.009",
      "name": "Boot or Logon Autostart Execution: Shortcut Modification (Appending URL to browser shortcuts)",
      "tactic": "Persistence"
    },
    {
      "id": "T1176",
      "name": "Browser Extensions (BHO installation)",
      "tactic": "Persistence"
    },
    {
      "id": "T1543.003",
      "name": "Create or Modify System Process: Windows Service (Watchdog service)",
      "tactic": "Persistence"
    }
  ],
  "containment_steps": [
    "Use the Windows Control Panel to uninstall the primary software bundle that delivered the Vosteran hijacker.",
    "Crucially, manually inspect and clean the properties of all web browser shortcuts (Desktop, Taskbar, Start Menu) to remove the appended Vosteran URL.",
    "Deploy an enterprise adware removal tool (like AdwCleaner) to locate and strip the deeply embedded registry hooks, BHOs, and watchdog services.",
    "Force a complete reset of all installed web browsers to factory defaults to clear the altered JSON preference files."
  ],
  "what_to_avoid": [
    "Do not rely solely on the browser's 'remove extension' button; the underlying watchdog service and modified shortcuts will immediately reinstall the hijacker.",
    "Avoid ignoring the infection; forced search routing can expose users to secondary malvertising and phishing attacks."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}