This book constitutes revised papers from the 6th International Workshop on Graphical Models for Security, GraMSec 2019, held in Hoboken, NJ, USA, in June 2019. The 8 full papers presented in this volume were carefully reviewed and selected from 15 submissions.

Invited Papers.- Graph Models in Tracking Behaviors for Cyber-Security.- Attack tree series: a case for dynamic attack tree analysis.- Attack Trees.- Attack trees: a notion of missing attacks.- Optimizing System Architecture Cost and Security Countermeasures.- Security Analysis of IoT systems using Attack Trees.- Attackdefense trees for abusing optical power meters: A case study and the OSEAD tool experience report.- Risk Management and Attack Graphs.- Quantifying and Analyzing Information Security Risk from Incident Data.- Poster Support for an Obeya-like Risk Management Approach.- Conceptual Abstraction of Attack Graphs - a Use Case of securiCAD.- High-level Automatic Event Detection and User Classification in a Social Network Context.