This book constitutes the proceedings of the Third International Conference on Human Aspects of Information Security, Privacy, and Trust, HAS 2015, held as part of the 17th International Conference on Human-Computer Interaction, HCII 2015, held in Los Angeles, CA, USA, in August 2015 and received a total of 4843 submissions, of which 1462 papers and 246 posters were accepted for publication aft…