In this paper we introduce a probabilistic-reasoning approach to detect Web robots (crawlers) from human visitors of Web sites. Our approach employs a Naive Bayes network to classify the HTTP sessions of a Web-server access log as crawler or human induced. The Bayesian network combines various pieces of evidence that were shown to distinguish between crawler and human HTTP traffic. The parameters of the Bayesian network are determined with machine learning techniques, and the resulting classification is based on the maximum posterior probability of all classes, given the available evidence. Our method is applied on real Web logs and provides a classification accuracy of 95%. The high accuracy with which our system detects crawler sessions, proves the robustness and effectiveness of the proposed methodology.
['Athena Stassopoulou', 'Marios D. Dikaiakos']
A probabilistic reasoning approach for discovering web crawler sessions