The United States Justice Department is increasing requirements for the use of cell phone tracking technology known as cellular-site simulators. The devices are known as Stingrays and are regularly used by municipal and federal law enforcement agencies across the United States. Since it mimics a regular cell phone tower, the device indiscriminately forces every mobile phone in its range to connect to it and captures the international mobile subscriber number (IMSI) and electronic serial number of users to reveal their location.  Privacy advocates claim that the primary issue with the  tracking technology is the indiscriminate nature with which it captures cellular phone data from innocent bystanders. 

In addition to tracking and locating mobile phone users, the technology is also used to intercept live communications or forcably turning off mobile phone functionality. NPR reports that "Under the new policy, federal investigators will be required to get a warrant from a judge demonstrating probable cause, in most domestic criminal probes. Agents will need to explain to judges how the technology is being used. And they'll be directed to destroy volumes of bystanders' data "no less than once daily." "

A representative of the American Civil Liberties Union reacted to the decision by stating that “After decades of secrecy in which the government hid this surveillance technology from courts, defense lawyers, and the American public, we are happy to see that the Justice Department is now willing to openly discuss its policies. Requiring the FBI, DEA, and other agencies to obtain a warrant before deploying these surveillance technologies — in most circumstances — is a positive first step."