Website Computer Detection

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.
• You can view your User-Agent string using a tool like WhatIsMyUserAgent.
• Example: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36
2. 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.

3. 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.