The two-volume set constitutes the refereed proceedings of the 5th International Conference on Big Data and Security, ICBDS 2023, held in Nanjing, China, during December 22-24, 2023. The 35 full papers and 1 short paper were carefully reviewed and selected from 161 submissions. They are organized in topical sections as follows: Part One: Big Data & New Method and Artificial Intelligence & Machine Learning Part Two: Data Technology & Network Security and IoT Security & Privacy Protection.