González Sánchez, RobertoJiang, LiliAhmed, MohamedMarciel Noguera, MiriamCuevas Rumín, RubénMetwalley, HassanNiccolini, Saverio2019-03-192019-03-192017-08TMA Conference 2017: Proceedings of the 1st Network Traffic Measurement and Analysis Conference, Dublin, Ireland, June 21-23, 2017, 9 pp.https://hdl.handle.net/10016/28205Proceeding of: 2017 Network Traffic Measurement and Analysis Conference (TMA)Users online are commonly tracked using HTTP cookies when browsing on the web. To protect their privacy, users tend to use simple tools to block the activity of HTTP cookies. However, the "block all" design of tools breaks critical web services or severely limits the online advertising ecosystem. Therefore, to ease this tension, a more nuanced strategy that discerns better the intended functionality of the HTTP cookies users encounter is required. We present the first large-scale study of the use of HTTP cookies in the wild using network traces containing more than 5.6 billion HTTP requests from real users for a period of two and a half months. We first present a statistical analysis of how cookies are used. We then analyze the structure of cookies and observe that; HTTP cookies are significantly more sophisticated than the name=value defined by the standard and assumed by researchers and developers. Based on our findings we present an algorithm that is able to extract the information included in 86% of the cookies in our dataset with an accuracy of 91.7%. Finally, we discuss the implications of our findings and provide solutions that can be used to improve the most promising privacy preserving tools.9application/pdfeng© 2017 IEEECookie recipeHTTP cookiesOnline usersWeb browsingBlock all designWeb servicesOnline advertising ecosystemNetwork tracesHTTP requestsPrivacy preserving toolsComputer network securityData privacyOnline front-endsTransport protocolsWeb servicesToolsPrivacyBrowsersEcosystemsEuropeAdvertisingWeb Pagesconference paperTelecomunicacioneshttps://doi.org/10.23919/TMA.2017.8002896open access19TMA Conference 2017: Proceedings of the 1st Network Traffic Measurement and Analysis Conference, Dublin, Ireland, June 21-23, 2017CC/0000028041