The Electronic Frontier Foundation (EFF) has released a free, open-source tool named Rayhunter that is designed to detect cell-site simulators (CSS), also known as IMSI catchers or Stingrays.

Stingray devices mimic legitimate cell towers to trick phones into connecting, allowing them to capture sensitive data, accurately geolocate users, and potentially intercept communications.

With the release of the Rayhunter, EFF seeks to give users the power to detect these instances, allowing them to protect themselves and also help draw a clearer picture of the exact deployment scale of Stingrays.