The US National Congress, which took place in August 2024 in Chicago, may have been a site of covert interception of telephone signals using a device known as a simulator of base stations. According to Wired, experts from the Electronic Frontier Foundation (EFF) discovered evidence of the operation of such a device, raising concerns about its legality and purpose.
Base station simulators, also called “stingrays,” intercept mobile data such as call metadata, location information, and internet traffic. These devices have been criticized by human rights activists for indiscriminately collecting data from all phones in the vicinity. The use of such technology could be employed to monitor protesters, particularly relevant during the mass demonstrations held at the congress amid simmering tensions.
Wired journalists decided to investigate the potential use of these devices during a political event. Using modified smartphones and tools like rayhunter developed by EFF, signals were tracked at key locations in Chicago. Initial analysis did not reveal clear signs of interception activities, but a subsequent study with improved detection methods produced different results.
Technical specialist EFF Cooper Quinin noted an anomaly on August 18, the day before the congress commenced. A device unexpectedly connected to a new tower, prompting the phone’s IMSI number (a unique mobile subscriber identifier) before terminating the connection—a pattern consistent with base station simulators.
While not definitive evidence, Quinin’s findings align with established behavior observed in controlled settings. The identity of the entity behind the device’s usage—be it US intelligence agencies, foreign entities, or private organizations—remains unknown.
In Illinois, the use of base station simulators requires a warrant, with federal agencies permitted to deploy them without authorization only in cases of immediate national security threats. However, a 2023 audit by the US Department of Homeland Security uncovered instances where such devices were utilized without proper oversight by secret service and national security investigation units.
The Chicago Police denied employing such technology during the congress, while the US Secret Service declined to reveal its operational methods citing heightened security protocols. Other Department of Homeland Security units and congress organizers chose not to comment on the matter.