The Bottom Line
In the settings we have talked about, law enforcement and counterterrorism, the fundamental problem is to detect the traces of adversaries and their activities in data, and use them to formulate responses. These responses could range from surveillance, to prevention or interdiction, to arrest or counterattack. We have seen that there are difficult issues when the response is proactive and preventive in nature, because much of the framework of law enforcement and prosecution is fundamentally reactive – punish bad activity after it happens, rather than prevent it before it happens. Of course, there is actually a broad continuum in conventional law enforcement, but many of the most difficult social issues, including widescale data collection and analysis, arise at the more proactive end of the continuum.