| Approaches in Anomaly-based Network Intrusion Detection Systems | p. 1 |
| Introduction | p. 1 |
| Anomaly-Based Intrusion Detection Systems | p. 2 |
| Payload-based vs header-based approaches | p. 4 |
| Setting up an ABS | p. 6 |
| Building the Model | p. 7 |
| Setting the threshold | p. 8 |
| PAYL and POSEIDON | p. 8 |
| PAYL | p. 8 |
| POSEIDON | p. 9 |
| Conclusions | p. 12 |
| Appendix | p. 13 |
| PAYL algorithm | p. 13 |
| SOM algorithm | p. 14 |
| References | p. 15 |
| Formal Specification for Fast Automatic Profiling of Program Behavior | p. 17 |
| Introduction | p. 17 |
| Related works | p. 19 |
| Methodology | p. 21 |
| Case Study | p. 22 |
| POP3 commands | p. 22 |
| The FSM (step 1) | p. 23 |
| VSP specification for ipop3d (step 2) | p. 24 |
| Compiling VSP (step 3) | p. 27 |
| Visiting the FSM1 (step 4) | p. 28 |
| Executing Traces (step 5) | p. 28 |
| Using the Methodology to Configure REMUS | p. 29 |
| Results | p. 30 |
| Concluding remarks | p. 31 |
| Appendix | p. 32 |
| The critical system calls | p. 32 |
| Postgres VSP Specification | p. 32 |
| References | p. 32 |
| Learning Behavior Profiles from Noisy Sequences | p. 39 |
| Introduction | p. 39 |
| Learning by Abstraction | p. 41 |
| Regular Expressions | p. 42 |
| String Alignment and Flexible Matching | p. 43 |
| The Learning Algorithm | p. 45 |
| [omega subscript S] Operator | p. 46 |
| [omega subscript I] Operator | p. 47 |
| Basic learning cycle | p. 48 |
| Refinement cycle | p. 50 |
| Evaluation on Artificial Traces | p. 51 |
| Motif reconstruction in presence of noise | p. 52 |
| Assessing the influence of alphabet size and motif length | p. 53 |
| Discovering graph structured patterns | p. 57 |
| User Profiling | p. 59 |
| Key Phrase Typing Model | p. 59 |
| Text Typing Model | p. 60 |
| Conclusion | p. 62 |
| References | p. 62 |
| Correlation Analysis of Intrusion Alerts | p. 65 |
| Introduction | p. 66 |
| Approaches Based on Similarity between Alert Attributes | p. 67 |
| Probabilistic Alert Correlation | p. 68 |
| Statistical Anomaly Analysis to Detect Stealthy Portscans | p. 69 |
| Root Cause Analysis | p. 70 |
| Statistical Causality Analysis Based Approach | p. 71 |
| Alert Clustering and Merging in MIRADOR Project | p. 72 |
| Approaches Based on Predefined Attack Scenarios | p. 74 |
| Aggregation and Correlation in IBM/Tivoli Systems | p. 74 |
| Chronicles Based Approach | p. 75 |
| Approaches Based on Prerequisites and Consequences of Attacks | p. 76 |
| Pre-condition/Post-condition Based Approach in MIRADOR Project | p. 77 |
| A Prerequisite and Consequence Based Approach | p. 78 |
| Attack Hypothesizing and Reasoning Techniques | p. 79 |
| Approaches Based on Multiple Information Sources | p. 82 |
| Mission-Impact-Based Approach | p. 83 |
| A Data Model M2D2 for Alert Correlation | p. 84 |
| Triggering Events and Common Resources Based Approach | p. 85 |
| Privacy Issues in Alert Correlation | p. 86 |
| An Approach on Alert Sharing and Correlation | p. 87 |
| Generalization and Perturbation Based Approaches | p. 88 |
| Summary | p. 90 |
| References | p. 90 |
| An Approach to Preventing, Correlating, and Predicting Multi-Step Network Attacks | p. 93 |
| Introduction | p. 93 |
| Related Work | p. 95 |
| Preliminaries | p. 97 |
| Attack Graph | p. 97 |
| Intrusion Alert and Correlation | p. 99 |
| Hardening Network To Prevent Multi-Step Intrusions | p. 100 |
| A Motivating Example | p. 100 |
| A Graph-Based Algorithm for Hardening A Network | p. 102 |
| Minimum-Cost Solutions | p. 106 |
| Correlating and Predicting Multi-Step Attacks | p. 108 |
| Motivation | p. 108 |
| Queue Graph-Based Alert Correlation | p. 109 |
| Hypothesizing Missing Alerts and Predicting Future Alerts | p. 114 |
| Compressing Result Graphs | p. 117 |
| Empirical Results | p. 119 |
| Effectiveness | p. 120 |
| Performance | p. 122 |
| Conclusion | p. 124 |
| References | p. 126 |
| Response: bridging the link between intrusion detection alerts and security policies | p. 129 |
| Introduction | p. 129 |
| Problem statement | p. 130 |
| Domain terminology | p. 130 |
| Intrusion Prevention and Response | p. 132 |
| Comprehensive Approach to Response | p. 133 |
| Security Policy Formalism | p. 133 |
| Choice of a Security Policy Formalism | p. 133 |
| The Or-BAC Formalism | p. 134 |
| Or-BAC Contexts | p. 136 |
| Presentation of a use case | p. 137 |
| Modelling of the use case | p. 139 |
| Applying Or-BAC for threat response | p. 144 |
| Examples of threat contexts | p. 144 |
| Atomic contexts | p. 148 |
| Composed contexts | p. 149 |
| Context activation | p. 151 |
| Context deactivation | p. 154 |
| Influence of Mapping on the Response Strategy | p. 154 |
| The Threat Response System | p. 155 |
| System Architecture | p. 155 |
| Alert Correlation Engine (ACE) | p. 155 |
| Policy Instantiation Engine (PIE) | p. 157 |
| Policy Decision Point (PDP) | p. 157 |
| Policy Enforcement Point (PEP) | p. 158 |
| From alerts to new policies | p. 158 |
| Syntactic mapping | p. 158 |
| Enrichment | p. 159 |
| Strategy application | p. 160 |
| Case Study: e-mail Server | p. 160 |
| Threats related to the use case | p. 161 |
| Threat analysis | p. 163 |
| Revised description of the Policy Components | p. 164 |
| Definition of the Security Policy | p. 165 |
| The Mapping Predicates | p. 167 |
| Issues with the Approach | p. 167 |
| Conclusion | p. 168 |
| References | p. 169 |
| Intrusion Detection and Reaction: an Integrated Approach to Network Security | p. 171 |
| Introduction | p. 172 |
| Related Work | p. 173 |
| Intrusion Detection Systems | p. 173 |
| Traceback | p. 176 |
| The Proposed Framework | p. 177 |
| An Architecture for Intrusion Detection | p. 178 |
| An Approach to Intrusion Detection | p. 179 |
| Performance evaluation | p. 188 |
| A Distributed Intrusion Detection System | p. 191 |
| Privacy Issues in Intrusion Detection | p. 193 |
| Intrusion Reaction: a System for Attack Source Detection | p. 195 |
| The ASSYST Architecture | p. 195 |
| Attack Sessions | p. 196 |
| The ASP Protocol | p. 197 |
| ASSYST: case studies | p. 197 |
| Intrusion detection subsystem | p. 201 |
| Traffic classification and intrusion reaction | p. 202 |
| ASSYST implementation details | p. 203 |
| ASP protocol implementation details | p. 204 |
| Testing the Approach | p. 205 |
| Conclusions and Future Work | p. 205 |
| References | p. 207 |
| Glossary of Terms Used in Security and Intrusion Detection | p. 211 |
| Index | p. 247 |
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