A process for detecting anomalous network traffic in a communications network, the process including: generating reference address distribution data representing a statistical distribution of source addresses of packets received over a first time period, the received packets being considered to represent normal network traffic; generating second address distribution data representing a statistical distribution of source addresses of packets received over a second time period; and determining whether the packets received over the second time period represent normal network traffic on the basis of a comparison of the second address distribution data and the reference address distribution data.