A Survey on Privacy and Security in Online Social Networks

Online Social Networks (OSNs) have become a mainstream cultural phenomenon for millions of Internet users. Combining user-constructed profiles with communication mechanisms that enable users to be pseudo-permanently “in touch”, OSNs leverage users’ real-world social relationships and blend even more our online and offline lives. As of 2014, Facebook had 1.32 billion monthly active users and it was the second most visited site on the Internet [Alexa, 2014]. Twitter, a social micro-blogging platform, claims over 500 million users [Holt, 2013]. According to Nielsen’s 2012 survey, social networking was the fourth most popular online activity [Nielsen, 2012]. Perhaps more than previous types of online applications, OSNs are blending in real life: companies are mining trends on Facebook and Twitter to create viral content for shares and likes; employers are checking Facebook, LinkedIn and Twitter profiles of job candidates1; law enforcement organizations are gleaning evidence from OSNs to solve crimes2; activities on online social platforms change political regimes [Lotan et al., 2011] and swing election results3. Because users in OSNs are typically connected to friends, family, and acquaintances, a common perception is that OSNs provide a more secure, private and trusted internet-mediated environment for online interaction [Cutillo et al., 2009b]. In reality, however, OSNs have raised the stakes for privacy protection because of the availability of an astonishing amount of personal user data which would not have been exposed otherwise. More importantly, OSNs expose now information from multiple social spheres – for example, personal information on Facebook and professional activity on LinkedIn – that, aggregated, leads to uncomfortably detailed profiles [Nissenbaum, 2011].