This week, criminology lecturer and researcher Bianca Fileborn talks about how women have been using social media to call out sexual harrassment and sexual assault. She also explains the reaction that women encounter when they mobilize and speak out on-line.Harassing behaviours online like trolling are shown to have psychological consequences similar to those of harassment offline. But who are the trolls, and why do they do it? Evita March, researcher and psychologist, takes a look at the dark side of social media.