We would get very few packets from each site. In this case, it analyzed packet flows over several months and revealed that many machines were being completely probed. After some time, all of the ports on each computer would have been systematically probed by several machines acting in concert. Once they gather a map of your network, they can then go back and target the machines that they've discovered. Assessing the real danger of this activity is difficult to do.
Many people use tools like the ping protocol to test and debug their networks.
In fact, those probing the military networks may be using the same tools used routinely by the network administrators, because they have both legitimate and illegitimate uses. Determining the scope of the hackers' effort is also hard, in part because the Department of Defense refuses to say much about them. The investigation is still unfolding and is also classified. The Pentagon has said that, as is the case with the vast majority of hacking attempts, the recent probes did not result in the penetration of any computers storing sensitive information. Also, the Dahlgren center said it found a way to thwart this method of probing, and has told all military services about the remedy.