Metadata is in the news right now: On Monday, the ACLU filed a legal challenge to the NSA's "metadata" phone monitoring program, which it alleges is both illegal and a violation of Americans' privacy.
The program doesn't literally listen into your calls. Rather, it looks at the data your calls generate for patterns that might indicate threats to national security.
President Obama defended the program on the basis that metadata is not the same as private data. Back in June he said:
"They are not looking at people’s names, and they’re not looking at content. But by sifting through this so-called metadata, they may identify potential leads with respect to folks who might engage in terrorism."
Should you be reassured?
Turns out such tiny bits of info, when gathered into sets of metadata, can have big potential repercussions, reports Ars Technica. Even without knowing the content of your calls, the pattern of them can entirely give away secrets of your private life.
For instance, the FBI figured out that General David Petraeus was having an affair with Paula Broadwell based on their email login habits, not the content of their emails.
The Electronic Frontier Foundation gives these three hypothetical examples:
They know you rang a phone sex service at 2:24 am and spoke for 18 minutes. But they don't know what you talked about.
They know you called the suicide prevention hotline from the Golden Gate Bridge. But the topic of the call remains a secret.
They know you spoke with an HIV testing service, then your doctor, then your health insurance company in the same hour. But they don't know what was discussed.
How long is each phone conversation? How many times a week do you call or text certain people? What time of day do you do so? How big a deal is it for the government to have a sense of how I use my phone, even if I never consented to it?
In the ACLU's suit, Princeton computer science professor Edward Felten argues that with computer technology getting more powerful all the time, metadata can be more useful than the micro-data underneath it:
This newfound data storage capacity has led to new ways of exploiting the digital record. Sophisticated computing tools permit the analysis of large data sets to identify embedded patterns and relationships, including personal details, habits, and behaviors.
Simply put, it's the abundance of metadata, and our perpetually increasing advanced ways of analyzing it, that render such value from so little. Ars Technica uses the example of a guy calling a bookie one time. The safe assumption is that he's placed a bet. But if we know that this guy called his bookie 20 times in two days, we can safely deduce that he's a gambling addict.
Working off of these data points, law enforcement can presumably build personality profiles based on phone habits and carry out their jobs more effectively in tracking down terrorists.
So yes, when the U.S. government examines your metadata, it does indeed learn a lot about your private life.