AAAI Publications, The Thirtieth International Flairs Conference

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A Text Mining Approach for Anomaly Detection in Application Layer DDoS Attacks
Maryam M Najafabadi, Taghi M. Khoshgoftaar, Chad Calvert, Clifford Kemp

Last modified: 2017-05-03

Abstract


Distributed Denial of Service (DDoS) attacks are a major threat to Internet security, with their use continuing to grow. Attackers are finding more sophisticated methods to attack servers. A lot of defense mechanisms have been proposed for DDoS attacks at IP and TCP layers. Those methods will not work well for application layer DDoS attacks that utilize legitimate application layer requests to overwhelm a webserver. These attacks look legitimate in both packets and protocol characteristics, which makes them harder to detect. In this paper, we propose an anomaly detection method to detect application layer DDoS attacks. We take a text mining approach to extract features which represent a user’s HTTP request sequence using bigrams. We apply the one class Support Vector Machine (SVM) algorithm on the extracted features from normal users’ HTTP request sequences. The one class SVM labels any newly seen instance that deviates from the normal, trained model as an application layer DDoS instance. We apply our experimental analysis on real web server logs collected from a student resource website. Three different variants of HTTP GET flood attacks are implemented on our server, generated via penetration testing. Our results show that the proposed method is able to detect application layer DDoS attacks with very good performance results.

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