That's an example of what Jebara's Columbia colleagues call "automated social hierarchy detection," a technique that can infer who gives the orders, who's respected and who's ignored based purely on whose emails get answered and how quickly. In 2007, they analyzed traffic from the Enron Corporation's email archive to correctly guess the seniority of several top-level managers.
Intelligence agencies may not need such tools to untangle corporate flowcharts, but identifying ringleaders becomes more important when tracking a suspected terrorist cell.
"If you piece together the chain of influence, then you can find the central authority," he said. "You can figure that out without looking at the content."
THEY'LL KNOW WHO YOU'RE TALKING TO
Seeing how networks of people communicate isn't just about finding your boss. It's about figuring out who your friends are.
Programs already exist to determine the density of communications — something that can identify close groups of friends or family without even knowing who's who. If one user is identified as suspicious, then users closest to him or her might get a second look as well.
"Let's say we find out somebody in the U.K. is a terrorist," said Kane. "You know exactly who he talks to on almost every channel, so BOOM you know his 10 closest contacts. Knowing that information not only allows you to go to his house, but allows you to go to their houses as well."
A SNOOPER'S CHARTER?
Detective work at the stroke of a key is clearly attractive to spy agencies. British officialdom has been pushing for a mass surveillance program for years. But civil libertarians are perturbed, branding the proposal a "snooper's charter."
Kane says the surveillance regime has to be seen in the context of social networks such as Facebook and LinkedIn, where hundreds of millions of people are constantly volunteering information about themselves, their friends, their family and their colleagues.
"There's no sense in getting all Big Brother-ish," he said. "The bottom line is that we're all leaving digital trails, everywhere, all the time. The whole concept of privacy is shifting daily."