Exposing the Hidden Web: An Analysis of Third-Party – HTTP Requests on One Million Websites. International Journal of Communication, October 2015. Timothy Libert.

“This article provides a quantitative analysis of privacy compromising mechanisms on one million popular websites. Findings indicate that nearly nine in ten websites leak user data to parties of which the user is likely unaware of; over six in ten websites spawn third-party cookies; and over eight in ten websites load Javascript code from external parties onto users’ computers. Sites which leak user data contact an average of nine external domains, indicating users may be tracked by multiple entities in tandem. By tracing the unintended disclosure of personal browsing histories on the web, it is revealed that a handful of American companies receive the vast bulk of user data. Finally, roughly one in five websites are potentially vulnerable to known NSA spying techniques at the time of analysis.”