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Linköping Studies in Science and Technology Thesis No. 1231 Adaptive Real-time Anomaly Detection for Safeguarding Critical Networks by Kalle Burbeck Submitted to Linköping Institute of Technology at Linköping University in partial fulfilment of the requirements for the degree of Licentiate of Engineering Department of Computer and Information Science Linköpings universitet SE-581 83 Linköping, Sweden Linköping 2006
Adaptive Real-time Anomaly Detection for Safeguarding Critical Networks by Kalle Burbeck February 2006 ISBN 91-85497-23-1 Linköping Studies in Science and Technology Thesis No. 1231 ISSN 0280-7971 LiU-Tek-Lic-2006:12 ABSTRACT Critical networks require defence in depth incorporating many different security technologies including intrusion detection. One important intrusion detection approach is called anomaly detection where normal (good) behaviour of users of the protected system is modelled, often using machine learning or data mining techniques. During detection new data is matched against the normality model, and deviations are marked as anomalies. Since no knowledge of attacks is needed to train the normality model, anomaly detection may detect previously unknown attacks. In this thesis we present ADWICE (Anomaly Detection With fast Incremental Clustering) and evaluate it in IP networks. ADWICE has the following properties: (i) Adaptation - Rather than making use of extensive periodic retraining sessions on stored off-line data to handle changes, ADWICE is fully incremental making very flexible on-line training of the model possible without destroying what is already learnt. When subsets of the model are not useful anymore, those clusters can be forgotten. (ii) Performance - ADWICE is linear in the number of input data thereby heavily reducing training time compared to alternative clustering algorithms. Training time as well as detection time is further reduced by the use of an integrated search-index. (iii) Scalability - Rather than keeping all data in memory, only compact cluster summaries are used. The linear time complexity also improves scalability of training. We have implemented ADWICE and integrated the algorithm in a software agent. The agent is a part of the Safeguard agent architecture, developed to perform network monitoring, intrusion detection and correlation as well as recovery. We have also applied ADWICE to publicly available network data to compare our approach to related works with similar approaches. The evaluation resulted in a high detection rate at reasonable false positives rate. This work has been supported by the European project Safeguard IST-2001-32685 and CENIIT (Center for Industrial Information Technology) at Linköping University. Department of Computer and Information Science Linköpings universitet SE-581 83 Linköping, Sweden
Acknowledgement First of all I would like to thank Simin Nadjm-Tehrani, my advisor. Without your guidance and support, this work would not have been possible. I am also grateful for all the fun we have had together during the Safeguard project. Too bad I did not take a picture when we exited the subway in Barcelona. Or when the storm forced us to sleep on the floor at a London airport and we experienced an overload of a critical communication infrastructure first hand when everybody tried to call home. Thanks to all colleges at RTSLAB for discussions and support. Keep the fika going or I will be forced to haunt you with my home made cakes. Special thanks go to Anne Moe, for your support with administrative problems, travels and organisation of events. Thanks also to Lillemor Wallgren, Britt-Inger Karlsson and Inger Norén for administrative help. Thanks to TUS for help with technical issues. This work was financially supported by the European project Safeguard IST-2001-32685 and CENIIT (Center for Industrial Information Technology) at Linköping University. Taking part in a large international project has sometimes been frustrating but most often instructive, challenging and fun. I am glad that I got the opportunity to take part in Safeguard. I would like to thank Tomas Lingvall, Thomas Dagonnier, Mikael Semling and Stefan Burschka and their colleagues at Swisscom for fruitful discussions and their many hours of work with the test network. Thanks also to Tomas for help with the Preprocessor and data generation. The Safeguard agent architecture has been developed with the input from all the research nodes of the project, the cooperation of whom is gratefully acknowl- edged. Special thanks to David Gamez and John Bigham from Queen Mary, Uni- versity of London and Oleg Morajko at AIA in Spain. Thanks to Wes Carter, our project coordinator. Thanks to Daniel Garpe and Robert Jonasson for your work with the agent platform evaluation. Thanks to Tobias Chyssler for your work with alert correla- tion engines. Also thanks to Tobias and Daniel for your help with implementing the correlation agent and for your company and many discussions during those hectic months of implementation phase in the project. Thanks to Sara Garcia Andrés for your first implementation of the simulation for our initial work on sur- vivability modelling. I would like to thank Henrik Larsson and Karin Ring for reading my thesis with fresh eyes. Doing PhD-studies while being a father of two wonderful small girls is not always easy. You have to learn to work very focused to get the maximum out of
those hours in your office, so that you also have time to spend with your family at home. I would like to thank my dear wife and very best friend Malin for all her help and support. Not the least for those weeks when conferences and project meetings have taken me far away from home. I love you with all of my heart. Thanks to Alva and Linnea for being such clever, cute and funny girls. Even when life sometimes is harsh, you often manage to make me smile. Thanks to my parents and Malin’s for your help with the girls and your support. Thanks also to our cuddly black cats Mashlul and Korlash, for lying and purring in my lap while I was writing those last hard chapters in the thesis. In context of my family I also would like to give special thanks to my advisor for her support not only with my licentiate studies, but also for supporting me in my private situation. Thanks for helping me being home those months with my girls in the middle of my studies. In the end I would like to thank all my friends and my family for my years of fun in Linköping. I will always remember those years as a very good time of my life. I dedicate this work to you all. Kalle Burbeck
CONTENTS Contents 1 Introduction . . . . . . . 1.1 Motivation . 1.2 Research challenges . . . 1.3 Contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 List of publications . . . . 1.5 Thesis outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix 1 1 3 5 6 7 2 Background . . . . . . . . . . . . . . . . . . . . 2.2 . . . . . . 2.1.1 Attack types . Intrusion detection . . 2.2.1 Components . 2.2.2 Taxonomy . 2.2.3 Evaluation metrics . . . . 2.1 Dependability and computer security . . . . . 9 9 . . 11 . 12 . 12 . 14 . 18 2.3 Software agents . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 . 22 2.4 Data mining and machine learning . . . . . . . . . . . . . . . . . 23 . 24 . 25 2.4.1 Classification . . 2.4.2 Clustering . . . . . . . . . . . . . . . . . 2.3.1 Agent platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 The Safeguard context 3.1 Critical infrastructures 3.2 Safeguard solutions . . . . . . . . . . . . . . 3.1.1 Telecommunications vulnerabilities . . 3.1.2 Electricity vulnerabilities . . . . . 31 . 31 . 33 . 33 . . 34 . 3.2.1 Agents for increased dependability . . 35 3.2.2 The Safeguard agent platform . . . . . . . . . . . . . . . 36 3.2.3 The Safeguard agent architecture . . 39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
x CONTENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 The Safeguard agents . . 3.3.1 Wrapper agent . 3.3.2 Hybrid detector agent . . . . . . 3.3.3 Topology agent . . . 3.3.4 Correlation agent . . 3.3.5 Human-machine interface agent . . 3.3.6 Action agent . 3.3.7 Actuator agent . 3.3.8 Negotiation agent . . . . 3.4 Safeguard test beds . . . . 42 . . 42 . . . . . . . . . . . . . . . . 43 . 44 . . . 44 . 49 . 52 . 53 . 53 . 54 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 ADWICE 4.1 Basic concepts . 4.2 Training . . . . . . . . . . . . 4.3 Detection . 4.4 Evaluation . . . . . . . . . . . . . 4.2.1 Using the original BIRCH index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 . 57 . . . . . . . . . . . . . . . . . . . . . . . 58 . 60 . . . . . . . . . . . . . . . . . . . . . . 61 . . . . . . . . . . . . . . . . . . . . . . . . 61 . . . . . . . . . . . . . . . . 63 . 66 . 67 . 68 . 70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1 Determining parameters 4.4.2 Detection rate versus false positives rate . . 4.4.3 Attack class results . . . 4.4.4 Aggregation for decreasing alert rate . 4.4.5 . . Safeguard scenarios . . . . . . . . . . . . . . . . 5 ADWICE with grid index . . . . . . . . . . 5.1.1 Influence of index errors . . 5.2 The grid-index . 5.3 Adaptation of the normality model . . 73 5.1 Problems of the original BIRCH index . . . . . . . . . . . . . . . 73 . 73 . . . . . . . . . . . . . . . . . . . . . . . 77 . 82 . 82 . . 82 . . . . . . . . . . . . . . . . . . . . . . 84 . 84 . 84 . 86 5.4.1 Detection rate versus false positives rate . . 5.4.2 5.4.3 . Incremental training . Forgetting . . . . Incremental training . Forgetting . . . 5.4 Evaluation . . . . . . . . 5.3.1 5.3.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Design . 6 Clustering hybrid detection agent . . . . . 6.1.1 Preprocessor 6.1.2 DataSource . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 . 88 . 89 . 92
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