The NSA is using billions of cellphone location records every day to track potential suspects worldwide, according to the latest leaks from government agency data, including the movements of US citizens despite not specifically going out of its way to collect them. "We are getting vast volumes" of information on cellphone location - amounting to records for hundreds of millions of individual devices - an NSA senior collection manager confirmed to The Washington Post, pointing to the agency's taps on international data cables that form the physical backbone of cellular networks.
Although the NSA's focus is on cellphone movement - and the relationships between devices and users of devices - abroad, the nature of the collection methodology means that also gathering some information on US citizens is inevitable. The legal position on retaining that data is murky, as long as it is collected "incidentally" rather than purposefully.
However, the NSA is allowed to collect data from US citizens when abroad with their handsets, though the intelligence agency insists that foreign targets are the primary concern.
According to the sources, the NSA's tracking tools are known as CO-TRAVELER and allow analysts to identify not only individuals but potentially unknown associates based on how they intersect. That possibility of pulling out important results from data hitherto believed to be generic has prompted the agency to stockpile masses of information "just in case"; according to one insider, the records amount to around 27 terabytes.
What proportion of that concerns the location of Americans is unclear, and the NSA says it has no way to calculate it. However, under no confusion is the extent to which the NSA is integrated into the mobile providers' systems: "the agency's access to carriers' networks appears to be vast" the Post concludes, while the leaked documents "indicate that the agency is able to render most efforts at communications security effectively futile."
For instance, the practice of using so-called "burnable" cellphones, effectively disposable handsets used for short periods, has led to CO-TRAVELER automatically flagging when a new phone connects to a cell tower in the short period after an older device is used for the very last time. Although not always a sign that a burner has been ditched, that's one possibility the NSA's systems highlight.
Even with the NSA tracking devices, the exact nature of what is being collected doesn't necessarily include the content of calls and messages. According to the leaks, the most common metadata is date, time, and location of an active cellphone, though the NSA systems can then combine multiple records and data on multiple devices to build up more comprehensive patterns of movement, interaction, and potential intent.
Meanwhile, the NSA has previously undertaken trials into cellphone tracking systems that not only would work in the US, but which the agency has suggested it would believe to be legal under the Patriot Act. Tests on the system did not result in a full launch, but it's unclear how many Americans were monitored as part of the dry-run.