On Modelling of Inter-dependent Network Infrastructures by Extended Leontief Models -- Critical Infrastructure Protection in Brazil - Threat Identification and Analysis -- Development of Information Security-Focused Incident Prevention Measures for Critical Information Infrastructure in Japan -- Design of a Mobile Agent-Based Adaptive Communication Middleware for Federations of Critical Infrastructure Simulations -- An Alternate Topology Generator for Joint Study of Power Grids and Communication Networks -- Trouble Brewing: Using Observations of Invariant Behavior to Detect Malicious Agency in Distributed Control Systems -- Optimisation of Critical Infrastructure Protection: The SiVe Project on Airport Security -- Cyber-Critical Infrastructure Protection Using Real-Time Payload-Based Anomaly Detection -- Decision Aid Tool and Ontology-Based Reasoning for Critical Infrastructure Vulnerabilities and Threats Analysis -- Application Filters for TCP/IP Industrial Automation Protocols -- Web Browser Security Update Effectiveness -- State-Based Network Intrusion Detection Systems for SCADA Protocols: A Proof of Concept -- Towards Early Warning Systems – Challenges, Technologies and Architecture -- CII Protection - Lessons for Developing Countries: South Africa as a Case Study -- Energy Theft in the Advanced Metering Infrastructure -- Current Capabilities, Requirements and a Proposed Strategy for Interdependency Analysis in the UK -- Stochastic Modelling of the Effects of Interdependencies between Critical Infrastructure.

This book constitutes the proceedings of the 4th International Workshop on Critical Information Infrastructures Security, CRITIS 2009, held in Bonn, Germany, during September 30 to October 2, 2009.