De nos jours, les réseaux sociaux ont considérablement changé la façon dont les personnes prennent des photos qu’importe le lieu, le moment, le contexte. Plus que 500 millions de photos sont partagées chaque jour sur les réseaux sociaux, auxquelles on peut ajouter les 200 millions de vidéos échangées en ligne chaque minute. Plus particulièrement, avec la démocratisation des smartphones, les utilisateurs de réseaux sociaux partagent instantanément les photos qu’ils prennent lors des divers événements de leur vie, leurs voyages, leurs aventures, etc. Partager ce type de données présente un danger pour la vie privée des utilisateurs et les expose ensuite à une surveillance grandissante. Ajouté à cela, aujourd’hui de nouvelles techniques permettent de combiner les données provenant de plusieurs sources entre elles de façon jamais possible auparavant. Cependant, la plupart des utilisateurs des réseaux sociaux ne se rendent même pas compte de la quantité incroyable de données très personnelles que les photos peuvent renfermer sur eux et sur leurs activités (par exemple, le cas du cyberharcèlement). Cela peut encore rendre plus difficile la possibilité de garder l’anonymat sur Internet dans de nombreuses situations où une certaine discrétion est essentielle (politique, lutte contre la fraude, critiques diverses, etc.).Ainsi, le but de ce travail est de fournir une mesure de protection de la vie privée, visant à identifier la quantité d’information qui permettrait de ré-identifier une personne en utilisant ses informations personnelles accessibles en ligne. Premièrement, nous fournissons un framework capable de mesurer le risque éventuel de ré-identification des personnes et d’assainir les documents multimédias destinés à être publiés et partagés. Deuxièmement, nous proposons une nouvelle approche pour enrichir le profil de l’utilisateur dont on souhaite préserver l’anonymat. Pour cela, nous exploitons les évènements personnels à partir des publications des utilisateurs et celles partagées par leurs contacts sur leur réseau social. Plus précisément, notre approche permet de détecter et lier les évènements élémentaires des personnes en utilisant les photos (et leurs métadonnées) partagées au sein de leur réseau social. Nous décrivons les expérimentations que nous avons menées sur des jeux de données réelles et synthétiques. Les résultats montrent l’efficacité de nos différentes contributions. / Today, social networking has considerably changed why people are taking pictures all the time everywhere they go. More than 500 million photos are uploaded and shared every day, along with more than 200 hours of videos every minute. More particularly, with the ubiquity of smartphones, social network users are now taking photos of events in their lives, travels, experiences, etc. and instantly uploading them online. Such public data sharing puts at risk the users’ privacy and expose them to a surveillance that is growing at a very rapid rate. Furthermore, new techniques are used today to extract publicly shared data and combine it with other data in ways never before thought possible. However, social networks users do not realize the wealth of information gathered from image data and which could be used to track all their activities at every moment (e.g., the case of cyberstalking). Therefore, in many situations (such as politics, fraud fighting and cultural critics, etc.), it becomes extremely hard to maintain individuals’ anonymity when the authors of the published data need to remain anonymous.Thus, the aim of this work is to provide a privacy-preserving constraint (de-linkability) to bound the amount of information that can be used to re-identify individuals using online profile information. Firstly, we provide a framework able to quantify the re-identification threat and sanitize multimedia documents to be published and shared. Secondly, we propose a new approach to enrich the profile information of the individuals to protect. Therefore, we exploit personal events in the individuals’ own posts as well as those shared by their friends/contacts. Specifically, our approach is able to detect and link users’ elementary events using photos (and related metadata) shared within their online social networks. A prototype has been implemented and several experiments have been conducted in this work to validate our different contributions.

This research provides insight into the use of social networks and social media by students at the Nelson Mandela Metropolitan University. The primary purpose of this research is to investigate student social media practices at NMMU to establish the reasons for students engaging in social media. A growing number of educators acknowledge the potential of social networking to (re)engage learners with their studies, while others fear that such practices compromise and disrupt student engagement with traditional education provision (Selwyn, 2009). This study, therefore, aims to identify how and for what reasons students use social networks and social media. This study attempts to provide answers to the following research questions: For which social networking sites do students register and actively engage in? What is the most popular social networking site for students? How often do students engage in social media practices? What is the main purpose for students engaging in social media practices? How do students gain access to social media? For what educational purposes can social media be used? For which business purposes can social media be used? Do students use social media to collaborate with peers and lecturers? Do students use social media to make buying decisions? The literature overview was conducted on social media and social networks from journals and books published between the periods 2003 to 2011 as the popularity of social media came to the forefront during this period. Topics researched included social networks and libraries, educational and business uses of social networking and social media. A quantitative study was considered to be most appropriate to conduct the research for this study; and non-probability sampling was the most appropriate given the size of the population and the nature of this research. xiv Students were invited to participate in the research by completing and submitting a survey questionnaire at the conclusion of their lectures in the second semester during the month of September. The data collected was then analysed using descriptive and inferential statistics to provide insight into student use of social media. The results would determine if relationships exist between the independent variables from the questionnaire, namely, age, gender, campus and course enrolment and the dependent factors, namely, usage, information exchange and security. This relationship would be determined for both the perceptions of social networking in general and the perceptions of NMMU social networking. These results are then used to identify further areas of research in the future. The majority of the population sample was between the ages of 17 and 21 and primarily females. The sample typically became aware of social media by means of word-of-mouth and accesses their social networking site/s more than five times a day. The main reason for registering and joining social networking sites was for social purposes. Furthermore, the sample used social networking sites for entertainment, social involvement, meeting new friends and maintaining relationships. The sample agreed that social networking makes information searching easier. The majority of the sample indicated that they were not registered on any NMMU Social Networking sites of the university or any faculty, department or unit social networking sites at the NMMU. However, it was clear that the majority of students was registered on social networking sites of some sort and would continue to use social networking and social media. The results from the study indicated that the mean value for the perceptions of social media in general were greater than that of the perceptions of NMMU social media in terms of usage. Likewise, the mean value for the perceptions of social networking in general was also greater than that of the perceptions of NMMU Social Networking for information exchange but the difference were very small. However, the mean value for the perceptions of NMMU Social Networking showed a greater mean value than that of the perceptions of social networking in general in terms of security. This means that respondents used social networking in general more than NMMU Social Networking. xv However, the respondents perceived NMMU Social Networking sites to be more secure than social networking sites in general. The results of this study could provide Higher Education Institutions in South Africa with the impetus to use social networks and social media to enhance students‟ learning experiences.

The Internet has shifted from the Web 1.0 era to the Web 2.0 era. In the contemporary era of web 2.0, the Internet is being used to build and reflect social relationships among people who share similar interests and activities. This is done through services such as Social Networking Sites (Facebook, Twitter etc.) and the web blogs. Currently, there is a very high usage of Social Networking Sites (SNSs) and blogs where people share their views, opinions, and thoughts. This leads to the production of a lot of data by people who post such content on SNSs. As a result, SNSs and blogs become the ideal platforms for opinion monitoring and the trend analysis. These SNSs and Blogs could be used by service providers for tracking what the public thinks or requires. The reason being, having such knowledge can help in decision making and future planning. If service providers can keep track of such views, opinions or thoughts with regard to the services they provide, they can better their understanding about the public or clients’ needs and improve the provision of relevant services. This research project presents a system prototype for performing opinion monitoring and trend analysis on Facebook. The proposed system crawl Facebook, indexes the data and provides user interface (UI) where end users can search and see the trending of a topics of their choice. The system prototype could also be used to check the trending topics without having to search. The main objective of this research project was to develop a framework that will contribute in improving the way government officials, companies or any service providers and normal citizens communicate regarding services they provide. This research project is premised on the conceptualization that if the government officials, companies or any service providers can keep track of the citizen’s opinions, views and thoughts with regards to services they provide it can help improve the delivery of such services. This research and the implementation of the trend analysis tool is undertaken in the context of the Siyakhula Living Lab (SLL), an Information and Communication Technologies for Development (ICTD) intervention for Dwesa marginalized community.

Social media has become an important means of everyday communication. It is a mechanism for “sharing” and “resharing” of information. While social network platforms provide the means to users for resharing/reblogging (aka retweeting), it remains unclear what motivates users to share. Predicting the spread of content is quite important for several purposes such as viral marketing, popular news detection, personalized message recommendation and on-line advertisement. Social content systems store all the information produced in the interactions between users. However, to turn this data into information that allows us to extract patterns, it is important to consider the different phenomena involved in these interactions. In this work, two phenomena that influence the evolution of networks are studied for Twitter: diffusion of information and communication among users. Previous studies have shown that history of interaction among users and properties of the message are good attributes to understand the retweet behavior of users. Factors like content of message and time are less investigated. We propose a prediction model for retweet actions of users. It formulates a function which ranks the users according to how receptive they are to a particular message. The function generates a confidence score for the edges joining the initiator of the message and the followers. Two different pieces of information propagate through different users in the network. We divide the task of calculating confidence score into two parts. The first part is independent of the test tweet. It models transmission rate of the tie between the initiator and the follower. We call this as ‘Pairwise Influence Estimation’. The second part incorporates the tweet properties and user activeness as per time in the ranking function. The proposed model exploits all the dimensions of information dif-fusion process-influence, content and temporal properties. We have captured local aspects of diffusion. It has been observed that users do not read all the messages on their site. This results in shortcomings in the above models. Considering this, we first study the temporal behavior of users’ activities, which directly reflects their availability pertaining to the upcoming post. Also, as it is a continuous task of predicting retweet behavior, we design a user-centric, and temporally localized incremental classification model by considering the fact that users do not read all their tweets. We have tested the effectiveness of this model by using real data from Twitter. We demonstrate that the new proposed model is more accurate in describing the information propagation in microblog compared to the existing methods. Our model works well when we consider different classes of users depending on their activity patterns. In addition, we also investigate the parameters of the model for different classes of users. We report some interesting distinguishing patterns in retweeting behavior of users.

El presente estudio plantea el paradigma en el que la orientación de la marca es en su totalidad el consumidor, sus emociones y deseos. Enfocándonos en el caso particular de la empresa de servicio Easy Taxi se demuestra, por medio del análisis de los comentarios negativos publicados en su página de Facebook, la apropiación de los mismos como oportunidades de mejora para la empresa. De esta manera se habla de la revalorización de la opinión del consumidor como un factor principal e influyente para cambios del servicio, la toma de decisiones y de estrategias de marketing. Esta apropiación se determina al definir los procesos internos de Easy Taxi, a través de entrevistas a los encargados de las áreas involucradas, la observación de la información expuesta en el fan page de la marca y la percepción del usuario por medio de encuestas. Así, se encuentra la relación entre los datos recogidos que afirma la importancia que hoy en día se le otorga a la queja dentro de las empresas por su exposición en los nuevos canales de comunicación. / Trabajo de investigación

The thesis is focused on describing the procedures through which organizations can acquire and retain high-quality long-term workers in the ICT sector. Most of the described procedures can be easily transfered to other industries. Brand new approaches that can be applied in the process of recruitment, are discussed as well, specifically, the possibility of using online social networks such as Facebook, LinkedIn or Twitter. Outsourcing is another, fairly new option of acquiring employees. An example of such a service is oDesk. The following part of the work describes the processes that are used in recruitment and retaining the skilled employees in the Unicorn company, which is the major producer of software in the Czech Republic. Despite Unicorn`s long-term achievements and experience in implementing the various human resources management and other related activities in order to acquire and maintain high-quality employees, the author was able to formulate specific proposals and recommendations that may contribute to their further improvement and streamlining. These recommendations are subject to the final part of the thesis.

We examined whether individual self-monitoring differences predict what type of relationships people have on Facebook. In the offline world, high self-monitors have large heterogeneous social networks made up of weak emotional ties, whereas low self-monitors have small homogenous social networks made up of strong emotional ties. In our study, we defined online relationships in terms of bridging and bonding social capital. Bridging social capital refers to large heterogeneous social networks made up of weak emotional ties. People maintain these relationships for social benefits. Bonding social capital refers to small homogeneous social networks made up of strong emotional ties. People maintain these relationships for emotional benefits. We predicted high self-monitors will have more bridging than bonding social capital on Facebook; low self-monitors will have more bonding than bridging social capital on Facebook. We believed attitudes about using Facebook would moderate these relationships. We used Snyder‟s Self-Monitoring Scale, Williams‟ Online Social Capital Scales, and Facebook Intensity Scale to assess our variables of interest. We found support for our hypotheses. For high self-monitors, greater importance placed on Facebook usage predicted increases in bridging social capital on Facebook; for low self-monitors, greater importance placed on Facebook usage predicted increases in bonding social capital on Facebook. Keywords: self-monitoring, social capital, social media, Facebook

Cette thèse s'intéresse particulièrement aux sites de vente en ligne et à leurs réseaux sociaux. La propension des utilisateurs utiliser ces sites Web tels qu'eBay et Amazon est de plus en plus importante en raison de leur fiabilité. Les consommateurs se réfèrent à ces sites Web pour leurs besoins et en deviennent clients. L'un des défis à relever est de fournir les informations utiles pour aider les clients dans leurs achats. Ainsi, une question sous-jacente à la thèse cherche à répondre est de savoir comment fournir une information complète aux clients afin de les aider dans leurs achats. C'est important pour les sites d'achats en ligne car cela satisfait les clients par ces informations utiles. Pour surmonter ce problème, trois études spécifiques ont été réalisées : (1) Trouver les utilisateurs influents, (2) Comprendre la propagation d'opinion et (3) Agréger les opinions. Dans la première partie, la thèse propose une méthodologie pour trouver les utilisateurs influents du réseau qui sont essentiels pour une propagation précise de l'opinion. Pour ce faire, les utilisateurs sont classés en fonction de deux scores : optimiste et pessimiste. Dans la deuxième partie, une nouvelle méthodologie de propagation de l'opinion est présentée pour parvenir à un accord et maintenir la cohérence entre les utilisateurs, ce qui rend l'agrégation possible. La propagation se fait en tenant compte des impacts des utilisateurs influents et des voisins. Enfin, dans la troisième partie, l'agrégation des avis est proposée pour rassembler les avis existants et les présenter comme des informations utiles pour les clients concernant chaque produit du site de vente en ligne. Pour ce faire, l'opérateur de calcul de la moyenne pondérée et les techniques floues sont utilisées. La thèse présente un modèle d'opinion consensuelle dans les réseaux. Les travaux peuvent s'appliquer à tout groupe qui a besoin de trouver un avis parmi les avis de ses membres. Par conséquent, le modèle proposé dans la thèse fournit un taux précis et approprié pour chaque produit des sites d'achat en ligne / Online Social Networks are increasing and piercing our lives such that almost every person in the world has a membership at least in one of them. Among famous social networks, there are online shopping websites such as Amazon, eBay and other ones which have members and the concepts of social networks apply to them. This thesis is particularly interested in the online shopping websites and their networks. According to the statistics, the attention of people to use these websites is growing due to their reliability. The consumers refer to these websites for their need (which could be a product, a place to stay, or home appliances) and become their customers. One of the challenging issues is providing useful information to help the customers in their shopping. Thus, an underlying question the thesis seeks to answer is how to provide comprehensive information to the customers in order to help them in their shopping. This is important for the online shopping websites as it satisfies the customers by this useful information and as a result increases their customers and the benefits of both sides. To overcome the problem, three specific connected studies are considered: (1) Finding the influential users, (2) Opinion Propagation and (3) Opinion Aggregation. In the first part, the thesis proposes a methodology to find the influential users in the network who are essential for an accurate opinion propagation. To do so, the users are ranked based on two scores namely optimist and pessimist. In the second part, a novel opinion propagation methodology is presented to reach an agreement and maintain the consistency among users which subsequently, makes the aggregation feasible. The propagation is conducted considering the impacts of the influential users and the neighbors. Ultimately, in the third part, the opinion aggregation is proposed to gather the existing opinions and present it as the valuable information to the customers regarding each product of the online shopping website. To this end, the weighted averaging operator and fuzzy techniques are used. The thesis presents a consensus opinion model in signed and unsigned networks. This solution can be applied to any group who needs to find a plenary opinion among the opinions of its members. Consequently, the proposed model in the thesis provides an accurate and appropriate rate for each product of the online shopping websites that gives precious information to their customers and helps them to have a better insight regarding the products.

Les services Internet populaires modèlent et remodèlent fondamentalement les moyens traditionnels de communication des personnes, ayant ainsi un impact majeur sur leur vie sociale. Deux des services Internet très populaires avec cette caractéristique sont les Réseaux sociaux en ligne (OSN) et les systèmes Peer-to-Peer (P2P). Les ONS fournissent un environnement virtuel où les gens peuvent partager leurs informations et leurs intérêts tout en étant en contact avec d'autres personnes. D'autre part, les systèmes P2P, qui sont toujours l'un des services populaires avec une grande proportion de l'ensemble du trafic Internet, offrent une occasion en or pour leurs clients de partager un type de contenu différent, y compris le contenu protégé. En dehors de l'énorme popularité des ONS et des systèmes de P2P parmi les utilisateurs réguliers, ils sont intensivement utilisés par les professionnels (grandes entreprises, politiciens, athlètes, célébrités en cas d'ONS et éditeurs de contenu professionnels en cas de P2P) afin d'interagir avec les gens à des fins différentes (campagnes marketing, les commentaires des clients, amélioration de la réputation publique, etc.) Dans cette thèse, nous caractérisons le comportement des utilisateurs réguliers et professionnels dans les deux services mentionnés populaires (ONS et P2P) en termes de stratégies de publication, de consommation de contenu et d'analyse comportementale. À cette fin, cinq de nos études menées sont présentées dans ce manuscrit comme suit: - "L'évolution des contenus multimédias", qui présente une analyse approfondie sur l'évolution du contenu multimédia disponible en BitTorrent en se concentrant sur quatre mesures pertinentes à travers différentes catégories de contenu : la disponibilité du contenu, la popularité du contenu, la taille de contenu et les commentaires de l'utilisateur - "La réaction des utilisateurs professionnels face aux actions de lutte contre le piratage", en examinant l'impact de deux grandes actions de lutte contre le piratage - la fermeture de Megaupload et la mise en œuvre de la loi anti-piratage française (HADOPI) - sur le comportement des publicateurs professionnels dans le plus grand portail de BitTorrent qui sont les principaux fournisseurs de contenu en ligne protégé. - "La quantité d'informations divulguées sur Facebook", en enquêtant sur l'exposition publique des profils utilisateurs, une grande base de données comprenant un demi-million d'utilisateurs réguliers. - "Les utilisateurs professionnels Cross Posting Activity», en analysant le modèle de publication des utilisateurs professionnels de mêmes informations sur trois grands ONS à savoir Facebook, Google+ et Twitter. - "Les stratégies des utilisateurs professionnels dans les ONS", où nous étudions la stratégie globale d'utilisateurs professionnels par secteur (par exemple, les entreprises de voitures, l'habillement, politiques, etc.) sur Facebook, Google+ et Twitter. Les résultats de cette thèse fournissent une vision d'ensemble pour comprendre certains aspects comportementaux importants de différents types d'utilisateurs des services Internet populaires et ces contributions peuvent être utilisées dans divers domaines (par exemple analyse de campagne marketing et publicité, etc.) et les différentes parties peuvent bénéficier des résultats et des méthodologies mises en œuvre telles que les FAI et les propriétaires des services pour leur planification ou l'expansion des services actuels à venir, ainsi que les professionnels pour accroître leur succès sur les médias sociaux / Popular Internet services are fundamentally shaping and reshaping traditional ways of people communication, thus having a major impact on their social life. Two of the very popular Internet services with this characteristic are Online Social Networks (OSNs) and Peer-to-Peer (P2P) systems. OSNs provide a virtual environment where people can share their information and interests as well as being in contact with other people. On the other hand, P2P systems, which are still one of the popular services with a large proportion of the whole Internet traffic, provide a golden opportunity for their customers to share different type of content including copyrighted content. Apart from the huge popularity of OSNs and P2P systems among regular users, they are being intensively used by professional players (big companies, politician, athletes, celebrities in case of OSNs and professional content publishers in case of P2P) in order to interact with people for different purposes (marketing campaigns, customer feedback, public reputation improvement, etc.). In this thesis, we characterize the behavior of regular and professional users in the two mentioned popular services (OSNs and P2P systems) in terms of publishing strategies, content consumption and behavioral analysis. To this end, five of our conducted studies are presented in this manuscript as follows: - “The evolution of multimedia contents", which presents a thorough analysis on the evolution of multimedia content available in BitTorrent by focusing on four relevant metrics across different content categories: content availability, content popularity, content size and user's feedback. - “The reaction of professional users to antipiracy actions", by examining the impact of two major antipiracy actions, the closure of Megaupload and the implementation of the French antipiracy law (HADOPI), on professional publishers behavior in the largest BitTorrent portal who are major providers of online copyrighted content. - “The amount of disclosed information on Facebook", by investigating the public exposure of Facebook users' profile attributes in a large dataset including half million regular users. - “Professional users Cross Posting Activity", by analyzing the publishing pattern of professional users which includes same information over three major OSNs namely Facebook, Google+ and Twitter. - “Professional Users' Strategies in OSNs", where we investigate the global strategy of professional users by sector (e.g., Cars companies, Clothing companies, Politician, etc.) over Facebook, Google+ and Twitter. The outcomes of this thesis provide an overall vision to understand some important behavioral aspects of different types of users on popular Internet services and these contributions can be used in various domains (e.g. marketing analysis and advertising campaign, etc.) and different parties can benefit from the results and the implemented methodologies such as ISPs and owners of the Services for their future planning or expansion of the current services as well as professional players to increase their success on social media

When the Supreme Court grants new rights, public awareness is a crucial part of enforcement. Gerald N. Rosenberg and Michael J. Klarman famously criticized minority rights organizations for attempting to gain new rights through the judiciary. The crux of their argument relied heavily on the American media's scanty coverage of Court issues and subsequent low public awareness of Court cases. Using the 2013 United States v. Windsor and Hollingsworth v. Perry rulings as a case study, I suggest that the media environment has changed so much since Rosenberg and Klarman were writing that their theories warrant reconsideration. Minority rights groups now have access to social media, a potentially powerful tool with which to educate the public about the Supreme Court and new rights granted by the Court.