This book constitutes the proceedings of the 4th International Conference on Science of Cyber Security, SciSec 2022, held in Matsu, Japan in August 2022. The 36 full papers presented in this volume were carefully reviewed and selected from 88 submissions. The papers are organized in the following topical sections: blockchain and applications; cryptography and applications; network security; cyber-physical system; malware; mobile system security; system and web security; security in financial industry; social engineering and personalized security; privacy and anonymity.