This volume constitutes the refereed proceedings of the 9th IFIP WG 11.2 International Conference(formerly Workshop) on Information Security Theory and Practices, WISTP 2015, held in Heraklion, Crete, Greece, in August 2015. The 14 revised full papers and 4 short papers presented together were carefully reviewed and selected from 52 submissions. WISTP 2015 sought original submissions from academia and industry presenting novel research on all theoretical and practical aspects of security and privacy, as well as experimental studies of elded systems, the application of security technology, the implementation of systems, and lessons learned. We encouraged submissions from other communities such as law, business, and policy that present these communities' perspectives on technological issues.