ClEveR: Clustering events with high density of true-to-false occurrence ratio

Leveraging the ICT evolution, the modern systems collect voluminous sets of monitoring data, which are analysed in order to increase the system's situational awareness. Apart from the regular activity this bulk of monitoring information may also include instances of anomalous operation, which need to be detected and examined thoroughly so as their root causes to be identified. Hence, for an alert mechanism it is crucial to investigate the cross-correlations among the suspicious monitoring traces not only with each other but also against the overall monitoring data, in order to discover any high spatio-temporal concentration of abnormal occurrences that could be considered as evidence of an underlying system malfunction. To this end, this paper presents a novel clustering algorithm that groups instances of problematic behaviour not only according to their concentration but also with respect to the presence of normal activity. On this basis, the proposed algorithm operates at two proximity scales, so as to allow for combining more distant anomalous observations that are not however interrupted by regular feedback. Regardless of the initial motivation, the clustering algorithm is applicable to any case of objects that share a common feature and for which areas of high density in comparison with the rest of the population are examined.