A system, method and computer program product for detecting distributed denial-of-service (DDoS) attacks is provided. Current aggregated flow information for a defined period of time is analyzed. It is determined whether network flow increased above a defined flow threshold value to a second data processing system connected to a network within the defined period of time based on analyzing the current aggregated flow information. In response to determining that the network flow has increased above the defined flow threshold value to the second data processing system connected to the network within the defined period of time, it is determined that the second data processing system is under a DDoS attack.