About the author: Kevin Hogan is the web content team leader for Technology Review, a magazine covering emerging technologies.

As the United States tries to grapple with the new realities of war and terrorism, questions for its intelligence community keep coming: How could something like [the terrorist attacks of] September 11, 2001, occur without plans being detected? Who was tracking the activities of suspected terrorists inside the country? How were they even here in the first place? What happened to those high-tech, Big Brother–type surveillance tools like the notorious global-communications eavesdropping network Echelon, or Carnivore, the FBI’s Internet snoopware, that were supposed to sniff out criminal activity"

For several decades, electronic systems have been quietly put in place to intercept satellite communications, tap...