1. A method of detecting web pages belonging to at least one similarity class from a plurality of web pages, the method comprising: determining clusters of the plurality of web pages based on characteristics of the content of the web pages; determining, for each of the determined clusters, at least one metric indicative of similarity among resource locators associated with the web pages of that cluster, wherein the metric indicative of similarity among resource locators is an entropy metric; and determining the web pages belonging to the at least one similarity class based on the determined clusters and the determined similarity metrics, including determining a cluster having web pages belonging to the at least one similarity class based on local entropy of selected keys of the resource locators for the web pages of that cluster and a statistical measure of the similarity metrics.