Terrorists are most likely like spies. At least one would think they would or should be. Spies have been around for a real long time, a real long time. The Persians had spies in Greece some 2500 years ago. So it is nothing new. Spies, and one would suspect Terrorists, communicate amongst one another and they would most likely do so in some secure manner, not say sending emails on some well known site or planning in an open "chat room". But perhaps they are really that dumb.
There is an article in Science which has alleged "experts" applauding the current administrations massive tactics of seeking these folks by examining what is in plain sight. In fact they state:
“I can tell you that this kind of thing is extremely effective,” says Alex Pentland, a computational social scientist at the Massachusetts Institute of Technology in Cambridge who has studied phone networks.
Now being told by someone from the Media Lab is not really that comforting to me but perhaps it may be somewhat truthful. I would not know what their basis is. The article continues:
The first step, Uzzi says, would be to map who calls whom—with each person represented by a point or “node” and each person-to-person link represented by a line or “edge”—to create a simple communication network. Next, the analyst would study details of calls—their frequency, duration, and timing—to determine how closely connected each pair of people is. This step breaks the communication network into smaller, overlapping social networks. The third step would be to study the dynamics of a social network, to see how activity ebbs and wanes and the network evolves. The fourth step would be to try to correlate the dynamics of the network with external events,
This assumes the "plain sight" scenario. If we take spies as the example, they have two options; hide in plain sight and be totally covert. When in plain sight you must be transparent, not attract attention, and be as if you were a sleeper. You could not stand out, you don't communicate, and you must fit in with everyone else. If you are covert than you stand apart and in this case you must use secure and covert means of communicating. Thus codes, secure comm links, such as wireless HF digital links, so that no one knows just who you are calling.
The use of the above techniques work well in commercial applications where people volunteer their information and have no desire to "hide". We can find that people say on Staten Island order more Pizza deliveries per 1,000 HH than any other area in the US and further that they have the greatest BMI in the US as well. But if we had some Chinese espionage agent I doubt that they would call the Embassy to transmit data. I would think.
I can recall all the means and methods of WW II and those in the Cold War, so why would they not be employed? Can we really detect those hiding in plain sight. Perhaps, but the Fort Hood terrorist was shouting out his plans and no one ever paid attention? What happened there. He apparently even gave presentations that should have alerted a Mall Guard.
Thus the issue is less the value than the very rights we would expect. As for Congress and its overview, I have found that all too often those providing oversight just do not have a clue technically so what good does it do.
I am still in favor of human intel, people, people where the action is. Again, just sitting in that bar in Istanbul, the coffee shop in Algiers, the shops in Islamabad. Words, accents, clothing, shoes, packages, hair cuts, people meeting, those are the tools of intel, and the ability to have a keen insight into the obvious.