Secret Phone Surveillance Tech Was Likely Deployed at 2024 DNC

A device capable of intercepting telephone signals was likely used during the 2024 Democratic National Convention (DNC) in Chicago, WIRED has learned, raising critical questions about who authorized its use and for what purpose.

The device, known as a cellular simulator, was identified by the Electronic Frontier Foundation (EFF), a digital rights organization, after analyzing wireless signal data collected by WIRED during an event in August.

Cell phone simulators imitate cell towers to intercept communications, indiscriminately collecting sensitive data such as call metadata, location information, and app traffic from all phones within range. Their use has drawn widespread criticism from privacy advocates and activists who argue such technologies could be used to secretly surveil protesters and suppress dissent.

The Democratic National Committee met amid widespread protests over Israel’s attack on the Gaza Strip. Bye prestigious influencers attended exclusive yacht parties and VIP eventsthousands of demonstrators clashed heavy law enforcement presenceincluding officers from the U.S. Capitol Police, Secret Service, Homeland Security Investigations, local sheriff’s offices and Chicago police.

Concerns about possible surveillance prompted WIRED to conduct First-of-its-kind wireless study to determine whether cell phone simulators are used. Reporters, equipped with two rooted Android phones and Wi-Fi hotspots running detection software, used Rayhunteris a tool developed by EFF to detect data anomalies associated with these devices. WIRED reporters tracked protest signals and event locations throughout Chicago, collecting extensive data during the political convention.

Initial tests conducted during the DNC did not reveal conclusive evidence of cellular simulator activity. However, several months later, EFF technologists reanalyzed the raw data using improved detection methods. The Rayhunter tool stores all interactions between devices and cell towers, allowing for deeper analysis as detection techniques evolve, according to Cooper Quintin, senior technologist at EFF.

The breakthrough came when EFF technologists used new heuristics to study situations where cell towers were asking devices for IMSI (International Mobile Subscriber Identity) numbers. According to an EFF analysis, on Aug. 18—the day before the convention officially began—the device WIRED reporters were carrying on their way to the hotel housing Democratic delegates from Midwestern U.S. states suddenly switched to a new tower. This tower queried the device’s IMSI and then immediately shut down, a sequence consistent with a cell phone simulator.

“This is extremely suspicious behavior that regular towers do not exhibit,” says Quintin. He notes that the EFF has typically only observed such patterns during simulated and controlled attacks. “This is not 100 percent smoking gun, but it is strong evidence that a cell phone simulator was deployed. We don’t know who is responsible – it could be the US government, foreign players or another organization.”

Illinois law requires law enforcement to obtain a warrant to use cell phone simulators. Likewise, federal agents, including Department of Homeland Security employees, are required to obtain warrants unless there is an immediate threat to national security. However, the DHS Inspector General in 2023 report found that both the Secret Service and Homeland Security did not always comply with these requirements.