A device capable of intercepting phone signals was likely deployed 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 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 the 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 can be exploited to covertly monitor protestors and suppress dissent.

The DNC convened amid widespread protests over Israel’s assault on Gaza. While credentialed influencers attended exclusive yacht parties and VIP events, thousands of demonstrators faced a heavy law enforcement presence, including 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 conduct a first-of-its-kind wireless survey to investigate whether cell-site simulators were being deployed. Reporters, equipped with two rooted Android phones and Wi-Fi hotspots running detection software, used Rayhunter—a tool developed by the EFF to detect data anomalies associated with these devices. WIRED’s reporters monitored signals at protests and event locations across Chicago, collecting extensive data during the political convention.

Initial tests conducted during the DNC revealed no conclusive...