Pilot tests of ThinThread proved almost too successful, according to a former intelligence expert who analyzed it. “It was nearly perfect,” the official says. “But it processed such a large amount of data that it picked up more Americans than the other systems.” Though ThinThread was intended to intercept foreign communications, it continued documenting signals when a trail crossed into the U.S. This was a big problem: federal law forbade the monitoring of domestic communications without a court warrant. And a warrant couldn’t be issued without probable cause and a known suspect. In order to comply with the law, Binney installed privacy controls and added an “anonymizing feature,” so that all American communications would be encrypted until a warrant was issued. The system would indicate when a pattern looked suspicious enough to justify a warrant.
But this was before 9/11, and the N.S.A.’s lawyers deemed ThinThread too invasive of Americans’ privacy. In addition, concerns were raised about whether the system would function on a huge scale, although preliminary tests had suggested that it would. In the fall of 2000, [General Michael Hayden, the director of the N.S.A.,] decided not to use ThinThread, largely because of his legal advisers’ concerns… .
I'm sure it discarded some things, but the basic technical control that ThinThread appeared to have that Trailblazer (and PRISM) lacked is cryptographic authorization controls.
The New Yorker's Mayer is paraphrasing an anonymous source, which she then counter-points in the very next sentence of the article with a quote from NSA historian Matthew Aid, who says: “The resistance to ThinThread was just standard bureaucratic politics. ThinThread was small, cost-effective, easy to understand, and protected the identity of Americans.” [1]
I think if you read my comments you'll find that I'm not denying that ThinThread had a goal of protecting the identity of Americans. The problem is that the collections programs underpinning PRISM and XKEYSCORE also have that goal. The problem isn't the technology.
Pilot tests of ThinThread proved almost too successful, according to a former intelligence expert who analyzed it. “It was nearly perfect,” the official says. “But it processed such a large amount of data that it picked up more Americans than the other systems.” Though ThinThread was intended to intercept foreign communications, it continued documenting signals when a trail crossed into the U.S. This was a big problem: federal law forbade the monitoring of domestic communications without a court warrant. And a warrant couldn’t be issued without probable cause and a known suspect. In order to comply with the law, Binney installed privacy controls and added an “anonymizing feature,” so that all American communications would be encrypted until a warrant was issued. The system would indicate when a pattern looked suspicious enough to justify a warrant.
But this was before 9/11, and the N.S.A.’s lawyers deemed ThinThread too invasive of Americans’ privacy. In addition, concerns were raised about whether the system would function on a huge scale, although preliminary tests had suggested that it would. In the fall of 2000, [General Michael Hayden, the director of the N.S.A.,] decided not to use ThinThread, largely because of his legal advisers’ concerns… .
I'm sure it discarded some things, but the basic technical control that ThinThread appeared to have that Trailblazer (and PRISM) lacked is cryptographic authorization controls.