WIRED has learned that a device capable of intercepting phone signals was deployed during the 2024 Democratic National Convention (DNC) in Chicago, raising important questions about who authorized its use and for what purpose. Was.
The device, known as a cell-site simulator, was identified by the Electronic Frontier Foundation (EFF), a digital rights advocacy organization, after analyzing wireless signal data collected by WIRED during an August event .
Cell-site simulators mimic cell towers to intercept communications, indiscriminately collecting sensitive data such as call metadata, location information, and app traffic from all phones within their range. Their use has drawn widespread criticism from privacy advocates and activists, who argue that such technology could be used to secretly monitor protesters and suppress dissent.
The DNC meeting was called amid widespread protests over Israel's attack on Gaza. Whereas Prestigious influencers attended exclusive yacht parties and VIP eventsthousands of protesters faced heavy law enforcement presenceThat includes officers from the US Capitol Police, Secret Service, Homeland Security Investigations, local sheriff's offices and Chicago Police.
Concerns over potential surveillance prompted WIRED to do so This is the first wireless survey of its kind to investigate whether cell-site simulators were being deployedReporters, equipped with two rooted Android phones and a Wi-Fi hotspot running detection software rehunter-A tool developed by EFF to detect data anomalies associated with these devices. WIRED journalists monitored signs at protests and event locations throughout Chicago, collecting extensive data during the political convention.
Initial tests conducted during DNC found no conclusive evidence of cell-site simulator activity. However, months later, EFF technologists reanalyzed the raw data using improved detection methods. According to Cooper Quintin, a senior technologist at EFF, the ReHunter tool stores all interactions between devices and cell towers, allowing for deeper analysis as detection technologies evolve.
A breakthrough came when EFF technologists applied a new heuristic to investigate situations where cell towers requested IMSI (International Mobile Subscriber Identity) numbers from devices. According to EFF's analysis, on August 18 – the day before the convention officially began – a device taken by WIRED reporters on their way to a hotel housing Democratic delegates from states in the US Midwest suddenly appeared in a new tower. Changed. That tower asked for the device's IMSI and then immediately disconnected – a sequence consistent with the operation of a cell-site simulator.
“This is extremely suspicious behavior that normal towers do not exhibit,” Quintin says. He noted that the EFF generally observed similar patterns only during simulated and controlled attacks. “This is not 100 percent irrefutable truth, but it is strong evidence that a cell-site simulator was deployed. “We don’t know who was responsible—it could have been the U.S. government, a foreign actor, or some other entity.”
Under Illinois law, law enforcement agencies must obtain a warrant to deploy cell-site simulators. Similarly, federal agents – including those from the Department of Homeland Security – are required to secure warrants unless an immediate national security threat exists. However, a 2023 DHS inspector general report found that both the Secret Service and Homeland Security Investigations did not always comply with these requirements.