An information processing device includes: an obtainer that obtains, from an anomaly detection sensor that detects an anomaly in a network, a detection log related to the anomaly in the network and the detection time of the anomaly indicated in the detection log; an occurrence time determiner that determines the occurrence time of an attack on the network based on the obtained detection time, and records the determined occurrence time; and an end time determiner that determines the expected end time of the attack on the network based on the obtained detection log, and records the determined expected end time.