The Department of Homeland Security has detected rogue devices that foreign spies and criminals could be using to track people's calls and texts in DC - Business Insider

The US government has detected rogue devices that foreign spies and criminals could be using to track cellphones and intercept calls and messages in Washington, DC. ...
http://www.businessinsider.com/foreign-spy-devices-in-washington-dc-tracking-calls-texts-2018-4