Slowing down to speed up: Protecting users against massive attacks in content distribution systems

The Internet has become a large platform where users can interact and share contents. In this context, content distribution systems (CDS) have been designed to satisfy users needs. Peer-to-Peer (P2P) systems have emerged as a prominent solution to speed up CDS. In this kind of distributed system, a particular interesting challenge refers to mechanisms employed to match user´s interests and published contents. The efficacy of CDS depends on the expertise of publishers to properly describe contents, which comprises an important task to guarantee good quality of experience (QoE) to users. Massive attacks may harm CDS if countermeasure mechanisms are not considered to fight content pollution. The main objective of the thesis is to devise a mechanism to provide users a good QoE and reduce the effect of malicious interference. To achieve that, three main steps guided the research work presented in the thesis and summarized in this paper: (i) we proposed a novel strategy that operates conservatively to avoid wide pollution dissemination, (ii) we extended our previous solution to cope with the subjectivity regarding content descriptions, and last, (iii) we proposed a generic model to investigate massive attacks (including content pollution) and conservative approaches.