If you're an American abroad, the NSA could find out where you are right now, if they wanted to. According to documents leaked by Edward Snowden, the agency's collecting 5 billion records a day on cell phone locations around the world. Some of those are from "incidentally" domestic cell phones.
The Washington Post just published the details of the latest revelation, and the details are hair-raising indeed. The suite of tools the NSA's using is known as CO-TRAVELER, and it's capable of tracking cell phones even when they're not being used. The paper says, "In scale, scope and potential impact on privacy, the efforts to collect and analyze location data may be unsurpassed among the NSA surveillance programs that have been disclosed since June."
The NSA maintains that this surveillance program, like the others, is totally legal and integral to catching foreign targets that represent a national security threat. And yet, everyday Americans are caught in the middle. The program tracks the locations of cell phones abroad as well as domestic cellphones that place calls abroad. Again, Americans traveling abroad can also be tracked. According to an internal briefing from May 2012, the agency has been collecting so much location information that the inflow was "outpacing [its] ability to ingest, process and store" the data.
Don't try to hide. Because if you do—say, by turning off your cell phone or switching cell phones—you'll raise red flags and attract more attention from the NSA. The agency is pulling data directly from the wires that connect mobile networks, much in the same way that it's allegedly tapping into the cables that connect Internet companies' data centers. As Chris Soghoian, principal technologist at the American Civil Liberties Union, put it, "The only way to hide your location is to disconnect from our modern communication system and live in a cave." God bless America. [Washington Post]