What Prism Knows: 8 Metadata Facts

One of the biggest worries triggered by Edward Snowden's National Security Agency (NSA) leaks concerns the scale of data being collected by the intelligence agency.

Government officials have said that while various NSA programs capture different types of data, including metadata relating to phone numbers and call duration, that information is used only to investigate foreigners, unless the FBI first convinces a judge to issue a warrant based on probable cause.

Still, the NSA appears to be collecting records on millions of innocent Americans, and then storing the information until it may be needed at a later date. The agency's supporters, including President Barack Obama, have said that the program makes the country more secure without compromising privacy. According to news reports, advanced search algorithms are used to ensure that information is accessed -- again, without a court order -- only on people who appear to be foreigners.

On the flip side, Center for Democracy and Technology (CDT) president and CEO Leslie Harris said, "There is no algorithm exception to the 4th Amendment," referring to the Constitution's prohibitions on unreasonable searches.

[ Is Edward Snowden a hero or a traitor -- or somewhere in between? Read NSA Prism Whistleblower Snowden Deserves A Medal. ]

Is either side fully right or wrong? Here are eight facts relating to the U.S. government's capture and use of metadata:

1. What Can Metadata Do?

For starters, Bruce Schneier, chief security technology officer of BT, said the metadata in question is more accurately known as "traffic analysis". Nomenclature aside, traffic analysis offers powerful possibilities for identifying whoever's behind the communications. A recently published Nature study found that human mobility traces are highly unique. Based on data collected by researchers on 1.5 million people over a 15-month period, given just four data points -- involving location and time -- they could uniquely identify 95% of the individuals, and by picking two random points, correctly identify half of the people being tracked.

2. Should Intelligence Agencies Be Allowed to Collect Everything?

What are the intelligence ramifications of the Nature study? "When paired with emerging 'big data' analytics techniques, metadata can ultimately prove to be more valuable, and potentially even more illuminating, than the 'data' itself," said CDT researcher Aubra Anthony in a blog post. "Right now, the government's interpretation of Patriot [Act] Section 215 doesn't seem properly limited to protect the privacy of innocent Americans. In fact, the collection of this metadata seems unlimited in scope and duration."

3. Obama: Collection Doesn't Equal Access

Many people have balked at having details related to every call they make recorded. But according to Obama, who's defended the NSA's programs, the data is rarely used. "If you're a U.S. person, then NSA is not listening to your phone calls and it's not targeting your emails unless it's getting an individualized court order," Obama told Charlie Rose in an interview broadcast Monday night on PBS.

Furthermore, Obama said, such a court order would result only if the FBI could demonstrate probable cause to a judge. "[It's] the same way it's always been, the same way when we were growing up and we were watching movies, you want to go set up a wiretap, you got to go to a judge, show probable cause."

4. Obama: This Program Doesn't Track Location Data

While a little location and time data could quickly allow investigators to create positive matches, according to President Obama, the NSA's phone-record interception program doesn't capture location data. "There are two programs that were revealed by Mr. Snowden, allegedly. ... Program number one, called the 2015 Program, what that does is it gets data from the service providers like a Verizon in bulk, and basically you have call pairs," Obama explained. "You have my telephone number connecting with your telephone number. There are no names. There is no content in that database. All it is, is the number pairs, when those calls took place, how long they took place. So that database is sitting there."

Given a "reasonable, articulable suspicion that this might involve foreign terrorist activity related to Al-Qaeda and some other international terrorist actors" -- perhaps from the CIA or New York Police Department -- then the NSA, with a court order, will perform narrow queries on the database to see if the phone number has been recorded, and if so, what other numbers it was used to contact. At that point, Obama explained, a related report will be generated and passed to the FBI. 5. What Location Information Does the NSA Capture?

Government officials have said that the 2015 Program -- also known as Mainway -- doesn't capture location metadata, and if it did, that might have Freedom of Assembly implications. But the NSA programs detailed to date in press reports have included not just Mainway and Prism, but also an Internet metadata collection program (Marina) and some type of telephone content interception program (Nucleon).

In his interview, Obama didn't touch on which NSA programs do record location data, leading The New Yorker to note: "There seems to be a shell game of reassurances, where what is meant to make us feel better about one program doesn't apply to another, or to how they work together."

6. Don't Stress over Meta-Data Collection?

How much metadata should the government be allowed to capture or use? "The drafters of the Constitution did not propose some absolute right to privacy; they ... saw privacy as a means to achieve a larger goal, to protect political liberties," said James A. Lewis, a senior fellow and director of the Technology and Public Policy Program at the Center for Strategic and International Studies, in a blog post.

His argument: if it safeguards people's political liberties, then capturing metadata is a useful technique. "The essential political rights are freedom of expression and assembly, freedom from arbitrary detention, and the right to petition the government for a redress of grievances," Lewis said. "If these four rights are protected, surveillance is immaterial in its effect on civil liberties."

7. NSA Focus: Terrorists, Nukes, Enemy Nations

Furthermore, Lewis said, while NSA might collect mountains of data, that's its charter, and in reality the agency reads almost none.

"NSA (and the larger U.S. intelligence effort) focuses the bulk of its attention on terrorism, proliferation, and a few hostile countries that threaten the United States and its allies." he explained. "These are the priorities; there simply are not enough analysts to look at much else."

8. Fears of a Surveillance State

But what of the potential impact of persistent -- and some might argue, excessive -- surveillance of innocent people? Without a doubt, the leaks have laid bare programs that many Americans have found to be overreaching.

"The programs of the past can be characterized as 'proximate' surveillance, in which the government attempted to use technology to directly monitor communication themselves," said the computer researcher known as Moxie Marlinspike, formerly CTO of Whisper Systems, in a blog post titled "We Should All Have Something To Hide."

"The programs of this decade mark the transition to 'oblique' surveillance, in which the government more often just goes to the places where information has been accumulating on its own, such as email providers, search engines, social networks, and telecoms," he said.

With persistent surveillance, Marlinspike said one fear is that by capturing so much information on U.S. citizens, a determined investigator could likely find some type of charges to file against a suspect, given that legal experts estimate that there could be almost 10,000 federal crimes on the books. "If the federal government had access to every email you've ever written and every phone call you've ever made, it's almost certain that they could find something you've done which violates a provision in the 27,000 pages of federal statues or 10,000 administrative regulations," said Marlinspike. "You probably do have something to hide, you just don't know it yet."