The US government has publicly acknowledged the existence of rogue surveillance devices in the country’s capital.
The mystery devices, known as Stingrays, are capable of tracking mobile phones and intercepting their calls and messages.
The US Department of Homeland Security (DHS) has not determined who is operating them or said how many of the devices there are.
Stingrays, nicknamed after a brand commonly used by US police departments, work by tricking phones into connecting with them by mimicking mobile phone towers.
The phones can then transmit identifying information to the devices, including their exact location, and even data from other phones that are nearby.
More advanced versions of the device eavesdrop on calls by making phones swap to unencrypted 2G wireless technology, while others try to plant malware.
The surveillance devices can range from the size of a briefcase to as small as a mobile phone, and cost anywhere from 1,000 to 200,000 US dollars.
Revealed after US Senator Ron Wyden sent a letter to the DHS, it’s the first time the US government has publicly acknowledged such devices’ existence in Washington.
Wyden said in a statement that “leaving security to the phone companies has proven to be disastrous” and that there is “clear evidence that our phone networks are being exploited by foreign governments and hackers”.