A disk-shaped recording medium includes a transparent substrate, and an optical recording layer formed on the transparent substrate. A color printer obtains measuring instrument information on measurement of a color in the image forming apparatus having the measuring sensor, and generates a chart image. If it is determined that the data associated with the network flow satisfy a first criterion based at least in part on a prediction value that reflects a likelihood that the network flow will result in a security event, the data associated with the network flow are begun to be recorded even though a second criterion corresponding to the security event has not been satisfied. Spin echoes are received that contain spurious ringing signals from the excitation and refocusing pulses.