Dianne Feinstein, a Democrat from liberal Northern California and the chairman of the Senate Select Committee on Intelligence, assured the public earlier today that the government’s secret snooping into the phone records of Americans was perfectly fine, because the information it obtained was only “meta,” meaning it excluded the actual content of the phone conversations, providing merely records, from a Verizon subsidiary, of who called whom when and from where. In addition, she said in a prepared statement, the “names of subscribers” were not included automatically in the metadata (though the numbers, surely, could be used to identify them). “Our courts have consistently recognized that there is no reasonable expectation of privacy in this type of metadata information and thus no search warrant is required to obtain it,” she said, adding that “any subsequent effort to obtain the content of an American’s communications would require a specific order from the FISA court.”

She said she understands privacy—“that’s why this is carefully done”—and noted that eleven special federal judges, the Foreign Intelligence Surveillance Court, which meets in secret, had authorized the vast intelligence collection. A White House official made the same points to reporters, saying, “The order reprinted overnight does not allow the government to listen in on anyone’s telephone calls” and was subject to “a robust legal regime.” The gist of the defense was that, in contrast to what took place under the Bush Administration, this form of secret domestic surveillance was legitimate because Congress had authorized it, and the judicial branch had ratified it, and the actual words spoken by one American to another were still private. So how bad could it be?

The answer, according to the mathematician and former Sun Microsystems engineer Susan Landau, whom I interviewed while reporting on the plight of the former N.S.A. whistleblower Thomas Drake and who is also the author of “Surveillance or Security?,” is that it’s worse than many might think.

“The public doesn’t understand,” she told me, speaking about so-called metadata. “It’s much more intrusive than content.” She explained that the government can learn immense amounts of proprietary information by studying “who you call, and who they call. If you can track that, you know exactly what is happening—you don’t need the content.”

For example, she said, in the world of business, a pattern of phone calls from key executives can reveal impending corporate takeovers. Personal phone calls can also reveal sensitive medical information: “You can see a call to a gynecologist, and then a call to an oncologist, and then a call to close family members.” And information from cell-phone towers can reveal the caller’s location. Metadata, she pointed out, can be so revelatory about whom reporters talk to in order to get sensitive stories that it can make more traditional tools in leak investigations, like search warrants and subpoenas, look quaint. “You can see the sources,” she said. When the F.B.I. obtains such records from news agencies, the Attorney General is required to sign off on each invasion of privacy. When the N.S.A. sweeps up millions of records a minute, it’s unclear if any such brakes are applied.

Metadata, Landau noted, can also reveal sensitive political information, showing, for instance, if opposition leaders are meeting, who is involved, where they gather, and for how long. Such data can reveal, too, who is romantically involved with whom, by tracking the locations of cell phones at night.

For the law-enforcement community, particularly the parts focussed on locating terrorists, metadata has led to breakthroughs. Khalid Sheikh Mohammed, the master planner of the September 11, 2001, attacks on New York and Washington, “got picked up by his cell phone,” Landau said. Many other criminal suspects have given themselves away through their metadata trails. In fact, Landau told me, metadata and other new surveillance tools have helped cut the average amount of time it takes the U.S. Marshals to capture a fugitive from forty-two days to two.

But with each technological breakthrough comes a break-in to realms previously thought private. “It’s really valuable for law enforcement, but we have to update the wiretap laws,” Landau said.

It was exactly these concerns that motivated the mathematician William Binney, a former N.S.A. official who spoke to me for the Drake story, to retire rather than keep working for an agency he suspected had begun to violate Americans’ fundamental privacy rights. After 9/11, Binney told me, as I reported in the piece, General Michael Hayden, who was then director of the N.S.A., “reassured everyone that the N.S.A. didn’t put out dragnets, and that was true. It had no need—it was getting every fish in the sea.”

Binney, who considered himself a conservative, feared that the N.S.A.’s data-mining program was so extensive that it could help “create an Orwellian state.”

As he told me at the time, wiretap surveillance requires trained human operators, but data mining is an automated process, which means that the entire country can be watched. Conceivably, the government could “monitor the Tea Party, or reporters, whatever group or organization you want to target,” he said. “It’s exactly what the Founding Fathers never wanted.”

Illustration by Matthew Hollister.

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