In this paper the use of Bandt and Pompe method and entropy are analyzed in order to detect the anomalous behaviors in a voice over IP (VoIP) system. Also, it is shown how the use of generalized entropies improves the anomalous behaviors detection by means of the entropic index. We use the entropic index in order to increase the variation between the entropy measure of normal and anomalous behavior, allowing us make a better discrimination and detection of anomalous behaviors.