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EFF – How Dozens of Companies Know You’re Reading About Those NSA Leaks

Follow up to previous postings on NSA’s big data domestic surveillance program via Micah Lee: “Each time your browser makes a request it sends the following information with it:

  • Your IP address and the exact time of the request
  • User-Agent string: which normally contains the web browser you’re using, your browser’s version, your operating system, processor information (32-bit, 64-bit), language settings, and other data
  • Referrer: the URL of the website you’re coming from—in the case of the Facebook Like button example, your browser tells Facebook which website you’re viewing
  • Other HTTP headers which contain potentially identifying information
  • Sometimes tracking cookies

Every company has different practices, but they generally log some or all of this information, perhaps indefinitely. It takes very little information about your web browser to build a unique fingerprint of it. See EFF’s Panopticlick website to see how unique and trackable your web browser is even without the use of tracking cookies. You can read more in our Primer on Information Theory and Privacy.”

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