A system including a first apparatus including a first processor, a first storage device, and a first communication interface and a second apparatus including a second processor and a second communication interface is provided. The first processor measures traffic of data communicated via a predetermined communication path in each of a plurality of time ranges, stores the data communicated in each of the plurality of time ranges in the first storage device, and performs a control processing to cause the first communication interface to transmit the measured data traffic to the second apparatus, and when the second processor receives the measured data, the second processor performs control processing to cause the second communication interface to transmit to the first apparatus designation information designating one of the plurality of time ranges in which protection target data not to be deleted from the first storage device has been communicated.