This book constitutes the proceedings of the 4th International Conference on Human Aspects of Information Security, Privacy, and Trust, HAS 2016, held as part of the 18th International Conference on Human-Computer Interaction, HCII 2016, held in Toronto, ON, Canada, in July 2016 and received a total of 4354 submissions, of which 1287 papers were accepted for publication after a careful reviewing process. These papers address the latest research and development efforts and highlight the human aspects of design and use of computing systems. The papers thoroughly cover the entire field of Human-Computer Interaction, addressing major advances in knowledge and effective use of computers in a variety of application areas. The 25 papers presented in the HAS 2016 proceedings are organized in topical sections as follows: human factors of authentication; security, privacy, and human behavior; and security technologies.