Representatives Eliot Engel, Frank Pallone Jr. and Bennie Thompson expressed concern over the recently revealed findings in their letter. "If these reports are true, it marks an incredible security vulnerability in the seat of the federal government," they wrote. "Critical federal agencies including those involved in national defense and intelligence operate in the Washington DC area, and these cell-site simulators could be surreptitiously intercepting the sensitive data of federal government employees at these agencies. Just as troubling, these foreign actors could be intercepting communications from American citizens."

They go on to note that the FCC has the authority to halt use of cell-site simulators as the agency in charge of commercial airwaves in the US. "Specifically, the Communications Act prohibits the very type of unauthorized transmissions that non-licensed cell-site simulators rely on to conduct surveillance," they said. "With no apparent evidence that these recently revealed unauthorized cell-site simulators are operating with an FCC license, it would seem the FCC need only to enforce the law to stop this foreign intelligence gathering."

Stingrays work by tricking cell phones into pinging a signal off of them instead of a cell tower. The devices can then hold onto that signal, allowing those using the device to track that phone and in some cases monitor calls and messages. In 2014, then FCC Chairman Tom Wheeler said that he had established a task force to combat unauthorized use of cell-site simulators, but a former advisor to Wheeler said that the task force had little political support. An FCC spokesperson told the Associated Press this week that the agency's role was to certify these devices, not require wireless carriers to protect their networks against them or crack down on their use.

The Representatives requested a quick response from the FCC and Chairman Ajit Pai.