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Connecting the Dots

Can the tools of graph theory and social-network studies unravel the next big plot?

Brian Hayes

The Plumber's Helper

It's in the nature of secret intelligence programs that most of us will never know for sure what the programs do, how well they work or even whether they exist. Nevertheless, in a democracy citizens can't entirely cede responsibility for what their government may be doing behind the black curtain. To have an informed opinion, we need to puzzle out the facts as best we can. Besides, it's an interesting puzzle.

My own opinion, so far, remains ill-formed. Tracking terrorists through call graphs looks like a hard problem. But just because I'm stumped certainly doesn't mean it can't be done!

Whether or not call graphs lead to hidden terrorist cells, they may be just the ticket for other tasks. Here's one idea. The Bush administration has expressed displeasure with the public disclosure of all the new surveillance programs, and would like to know who leaked the news. The call graph might be an ideal device for answering that question. One need merely list, on the one hand, all those who had access to the information, and on the other hand the journalists who ultimately reported the story. Search in the graph for direct or indirect connections between those two sets of vertices. The irony is that whoever released the information probably understood quite clearly this potential for exposure.

© Brian Hayes

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