The book presents novel research in the areas of social identity and security when using mobile platforms. The topics cover a broad range of applications related to securing social identity as well as the latest advances in the field, including the presentation of novel research methods that are in the service of all citizens using mobile devices. More specifically, academic, industry-related and government (law enforcement, intelligence and defence) organizations, will benefit from the research topics of this book that cover the concept of identity management and security using mobile platforms from various perspectives, i.e. whether a user navigates to social media, accesses their own phone devices, access their bank accounts, uses online shopping service providers, accesses their personal documents or accounts with valuable information, surfs the internet, or even becomes a victim of cyberattacks. In all of the aforementioned cases, there is a need for mobile related technologies that protect the users' social identity and well-being in the digital world, including the use of biometrics, cybersecurity software and tools, active authentication and identity anti-spoofing algorithms and more.