An apparatus for detecting a distributed denial-of-service (DDoS) attack in a networked computing system includes at least one detector in operative communication with a corresponding router in the networked computing system. The detector is configured: to receive data packets from the router; to compare a volume of the data packets received by the detector with a threshold value; to obtain an Autonomous System Number (ASN) associated with a source Internet Protocol (IP) address of the received data packets when the volume of the data packets exceeds the threshold value; and to generate an output signal indicative of a probability of a presence of a DDoS attack based at least in part on threat information corresponding to the ASN associated with the source IP address of the received data packets.