This volume contains the revised version of the papers presented at the 5th International Symposium on Foundations and Practice of Security (FPS 2012). The symposium was held at ETS (Ecole de technologie supérieure), in Montréal, Canada, during October 25-26, 2012. The event covered a wide and rich spectrum of research in different areas of theoretical and practical security solutions for information systems. In response to the call for participation, 62 papers from 28 different countries were submitted to FPS 2012. These submission were evaluated on the basis of their significance, novelty, and technical quality. All submissions went through a careful anonymous review process (three or more reviews per submission) aided by 55 Technical Program Committee members and 32 external referees. In the end, 22 full papers, accompanied by three short papers, were presented at the event. The final program also included two invited talks by Douglas Stinson (University of Waterloo, Canada) and Ana Rosa Cavalli (TELECOM & Management SudParis, France). Our special thanks to Douglas and Ana for accepting our invitation and for their presence during the event and talks.