An information processing apparatus sends a management apparatus execution information about processes that the information processing apparatus has executed while performing a task in response to an instruction from the management apparatus. The management apparatus stores the received execution information in a storage unit. A security detection program monitors the information processing apparatus, and when detecting an alert, sends alert information including information about a process or command being executed by the information processing apparatus, to the management apparatus. The management apparatus receives the alert information, and performs filtering of determining, on the basis of a schedule and the execution information, whether the alert information relates to a task that the management apparatus has instructed the information processing apparatus to perform.