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CHAPTER 1
INTRODUCTION
The Internet has created never before seen opportunities for human interaction and
socialization. In the past decade, social media, in particular, has had a popularity explosion.
From MySpace to Facebook, Twitter, Flickr, and Instagram, people are connecting and
interacting in a way that was previously impossible. The widespread usage of social
media across people from all ages created a vast amount of data for several research topics,
including recommender systems [54], link predictions [37], visualization, and analysis of
social networks [6].
1.1 Motivation
While the growth of social media has created a good platform for communications
and information sharing, it has also created a new platform for malicious activities such
as spamming [25], trolling [8], and cyberbullying [32]. According to the Cyberbullying
Research Center (CRC) [44], cyberbullying occurs when someone uses the technology to
send messages to harass, mistreat or threaten a person or a group. Unlike traditional
bullying where aggression is a short and temporary face to face occurrence, with cyber-
bullying, the bullying messages are always present online, can be accessed worldwide,
and are often irrevocable. A series of surveys done by the CRC shows that the rates of
cyberbullying among youth have increased over the past nine years, going from 18.8% in