The decision within a packet processing device to transmit a newly arriving packet into a queue to await further processing or to discard the same packet is made by a flow control method and system. An evaluation value of an AE is calculated from a result of the monitoring, and if the result of the calculation shows that the image is not in low luminance, data in each of the fields is read out by carrying out an exposure, and a normal process for a still image is performed. Each resilient portion forms a protrusion. The device profiler traverses a vulnerability tree having nodes representative of characteristics of the hosts, each node having an associated set of potential vulnerabilities.