With the global diffusion of Internet, the number of actions and operations performed online has increased exponentially: for example, e-commerce is the preferred means for shopping nowadays, while Google Maps seems to have definitely replaced the traditional paper maps. Behind all these useful services, organizations that own websites are involved in a profitable data market, where users' data are sold by publishers to vendors. In this way, data buyers try to understand users' behaviour in order to present them the most suitable ads according to their recent online activity. The publication of the GDPR in May 2018 however focused the attention of companies and especially users on the possible security and privacy issues that can emerge while browsing the Internet.