US law enforcement agencies have partnered with a company that gives it the ability to track mobile location data without ever having to secure a warrant.

According to a report from Protocol, federal law enforcement in the US have signed a contract to use a tool called Locate X, made by the company Babel Street, that allows one to track the prior and future travels of mobile devices that pass through specific geographic areas.

Specifically, Locate X allows users to 'geo-fence' an area, meaning they're able to set up geographical parameters in which any passing device's location data can be hoovered up.

Law enforcement have parented with Babel Street, makers of Locate X, a tool that allows its wielders to hoover up location data from devices that enter a pre-determined geo-fence (stock)

This allows the wielder to see where a device has been and also where it travels to after being picked up by Locate X.

Protocol reports that the tool can see user data going back months and gleans all of its information - the same data used by popular cell phone apps for targeted ads - anonymously.

Among the agencies reportedly in contract to use the tool are U.S. Customs and Border Protection, Secret Service and U.S. Immigration and Customs Enforcement, according to federal records obtained by Protocol.

According to Protocol, the company's federal contracts exceeded $5 million in 2018.

While none of the agencies connected to using the tool confirmed their use, Protocol reports that a former government source familiar with the technology described how Locate X might factor into a potential terrorist situation.

For instance, law enforcement may use Locate X to geo-fence an area surrounding a a bombing after the attack takes place to hoover up the location data of mobile devices near the area.

They could then look through that data to see prior travels as well as where the device traveled afterwards.

'If you see a device that a month ago was in Saudi Arabia, then you know maybe Saudis were involved,' the source told Protocol.

'It's a lead generator. You get a data point, and from there you use your other resources to figure out if it's valid.'

Babel Street has reportedly made a concerted effort to keep the existence of Locate X a secret by choosing not to mention it in marketing materials and referring to tool as 'confidential' in government contracts.

Babel Street has made it clear that partners are not allowed to discuss Locate X or use the data in a court of law (Stock)

The company also stipulates that Locate X is designed for 'research purposes only' and forbids law enforcement from using any data gleaned from the tool as evidence or mentioning it in court, Protocol reports.

While law enforcement's use of Locate X isn't explicitly illegal, it does seem to butt up against a Supreme Court ruling, Carpenter v. United States, that dictates law enforcement must, in most cases, obtain a search warrant before accessing one's cell tower data relating to individual accounts.

In response to a request from Protocol, however, a lawyer the the American Civil Liberties Union (ACLU) Nathan Wessler, argued that since the use of Locate X is kept secret, it violates precedents outlined by Carpenter v. United States.

'These secrecy provisions prevent the courts from providing oversight,' Wessler told Protocol.

'That is really corrosive to our system of checks and balances.'

Other privacy experts interviewed by Protocol say Locate X's use subverts legal authority.

'That consumers can have data being collected that tracks their location, and the government, instead of getting a warrant, which they would normally need to do, can just go to a private company and buy it directly, that's hugely concerning,' Serge Egelman, a computer science professor at UC Berkeley who works on privacy issues told Protocol.