Blog | G5 Cyber Security

Website Computer Detection

G5 Cyber Security

TL;DR

A website can detect some information about a computer, but it can’t remotely operate it directly. Websites primarily use the User-Agent string and browser fingerprinting to gather details. They cannot take control of your machine without you installing something (like Remote Desktop software) or falling for a scam.

How Websites Detect Computer Information

  1. User-Agent String: This is the most common method. Your browser sends this string to websites, identifying the browser type, version, operating system, and sometimes device information.
  • Browser Fingerprinting: This is more advanced. Websites collect various pieces of information about your browser and computer configuration to create a unique ‘fingerprint’. This includes:
    • Installed fonts
    • Supported MIME types
    • Timezone
    • Screen resolution
    • Plugins installed (Flash, Java – increasingly rare)
    • Do Not Track settings
    • Language preferences

    Browser fingerprinting is harder to block completely as it relies on many different data points. Tools like EFF’s Panopticlick can show you how unique your browser fingerprint is.

  • JavaScript: Websites use JavaScript code to gather information about the browser and operating system. This is often used in conjunction with fingerprinting.
    • Example (detecting OS): 
      if (navigator.platform.indexOf('Win') != -1) {
  document.write("You are using Windows");
} else if (navigator.platform.indexOf('Mac') != -1) {
  document.write("You are using macOS");
}

    • What Websites *Cannot* Do

    1. Direct Remote Control: A website cannot directly take control of your computer without your explicit permission. This requires software installed on your machine (like TeamViewer, AnyDesk, or Remote Desktop) or a malicious program you’ve downloaded.
    2. Access Files Without Permission: Websites running in a browser sandbox have limited access to your file system. They can’t browse your files without you specifically choosing to upload them.
    3. Install Software Automatically: Websites cannot install software on your computer without your interaction (e.g., clicking a download button and granting permissions).

    Protecting Your Privacy

    1. Keep Your Browser Updated: Updates often include security patches that protect against fingerprinting techniques.
    2. Use Privacy-Focused Browsers: Browsers like Brave, Firefox Focus, and Tor are designed to minimize tracking.
    3. Install Privacy Extensions: Extensions like uBlock Origin (blocks trackers), Privacy Badger (learns to block trackers automatically) and NoScript (blocks JavaScript) can help.
    4. Disable Unnecessary Plugins: Remove or disable plugins you don’t use, as they can be exploited for fingerprinting.
    5. Be Careful What You Download: Only download software from trusted sources.
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