The Democratic National Convention, held in August 2024 in Chicago, may have been the site of clandestine use of a device designed to intercept cellular signals. According to WIRED, experts from the Electronic Frontier Foundation (EFF) detected signs suggesting the operation of a so-called cell-site simulator, raising questions about its legality and purpose.
Cell-site simulators, often referred to as “IMSI catchers” or “stingrays,” intercept mobile data, including call metadata, location, and internet traffic. These devices are frequently criticized by civil rights advocates for their indiscriminate nature, as they capture information from all phones within range. Such technology could be deployed for surveillance of protesters, a particularly relevant concern given the mass demonstrations during the convention amid the Gaza conflict.
WIRED sought to investigate whether these devices were employed during the political event. Reporters equipped with modified smartphones and Rayhunter—a detection tool developed by the EFF—monitored signals at key locations in Chicago. Initial data analysis did not reveal any conclusive evidence of interceptors. However, subsequent analysis months later, using enhanced detection methods, yielded different results.
According to EFF technologist Cooper Quintin, an anomaly was identified on August 18, one day prior to the convention’s commencement. One of WIRED’s devices unexpectedly connected to a new cell tower, which requested the phone’s IMSI number (a unique mobile subscriber identifier) before severing the connection. Such behavior is characteristic of cell-site simulators.
Quintin emphasized that while this is not definitive proof, the findings align with the operational patterns of such devices under laboratory conditions. The identity of those operating the equipment—whether U.S. intelligence agencies, foreign spies, or private entities—remains unclear.
In Illinois, the use of cell-site simulators requires a warrant, while federal agencies can deploy them without authorization only in cases of immediate national security threats. However, a 2023 audit by the U.S. Department of Homeland Security revealed instances where the Secret Service and Homeland Security Investigations used these devices without adequate oversight.
Chicago police told WIRED they did not employ such technologies during the convention. The U.S. Secret Service declined to comment on its operational methods, citing protocols for high-security events. Other DHS agencies and convention organizers refrained from providing responses.
EFF has previously documented similar anomalies in Washington, D.C., particularly in areas with high concentrations of embassies and diplomatic missions. In 2019, the FBI accused Israel of deploying a cell-site simulator near the White House, an allegation that Israeli officials denied.
The question of whether participants in the protests during the Democratic National Convention were subject to surveillance remains unanswered, but civil rights advocates consider the ambiguity surrounding this technology deeply troubling. Nate Wessler, Deputy Director of the ACLU’s Speech, Privacy, and Technology Project, warned that even the possibility of covert monitoring could suppress free expression and stifle civic engagement.
