Abstract: Users tracking activities and targeted advertising on social networks have been the subject of criticism for psycho-social reasons, but we note that after the entry into force of the General Regulation on the protection of data, European courts have not hesitated to sanction these practices. In this article, we conduct a comparative analysis of the privacy policies of the main social networks by examining the conditions for collecting information about their users, but not only users, and using them for advertising purposes. Considering the case of Cambridge Analytica, beyond the political interests at stake, we understand from the analysis of the past facts that the passive surveillance of users using various social platforms has moved to a form of active control of their lives and the social structures built organically by the people. The automated processing of the users profiles and the targeted recommendation of only certain types of messages, respectively, people, puts in danger the freedom to choose itself.

Key-words: social networks; tracking; targeted advertising; profiling; data protection.