This volume contains the papers presented at the 23rd Annual IFIP WG 11. 3 Working Conference on Data and Applications Security (DBSEC) held at C- cordia University, Montreal, Canada, July 12 15, 2009. This year s working conference continued its tradition of being a forum for disseminating original research results and practical experiences in data and applications security. This year we had an excellent program consisting of 9 research paper s- sionswith 18 full researchpapers, and 4 shortpaperswhich were selected froma total of 47 submissions after a rigorous reviewing process by the...