This book constitutes the refereed proceedings of the 24th Nordic Conference on Secure IT Systems, NordSec 2019, held in Aalborg, Denmark, in November 2019. The 17 full papers presented in this volume were carefully reviewed and selected from 32 submissions. They are organized in topical sections named: privacy; network security; platform security and malware; and system and software security.

This Festschrift volume is published in honor of Hanne Riis Nielson and Flemming Nielson on the occasion of their 60th birthdays in 2014 and 2015, respectively. The papers included in this volume deal with the wide area of calculi, semantics, and analysis. The book features contributions from colleagues, who have worked together with Hanne and Flemming through their scientific life and are dedicated to them and to their work. The papers were presented at a colloquium at the Technical University of Denmark in January 2016.