What Wi-Fi Devices Are Nearby? Any Cameras Watching Me?

Caleb Madrigal opens with a refresher on Wi-Fi as a radio technology. Networks sit on channels in the 2.4 and 5 GHz bands, and the talk focuses on the data link layer, where MAC addresses identify network interfaces. He explains monitor mode, which receives frames without joining a network. Traffic captured this way stays encrypted, but frame headers still expose addresses, frame types, network names and received signal strength.

The motivation was a home camera that kept uploading video while it was disarmed, which led him to build trackerjacker, an open-source Python tool. The demo covers a mapping mode that hops across channels and records networks, connected devices, power levels and vendor prefixes into a YAML file. He also shows the plugin interface, including a fox-hunting plugin that follows the strongest signal and a plugin that counts device manufacturers.

He closes with practical takeaways. Vendor information makes it possible to spot particular cameras and other devices without connecting to their networks, and bursts of upload traffic can reveal activity. Phones leak identifiers through probe requests. Randomized addresses help until a device connects, so turning Wi-Fi off while travelling reduces exposure. The tool currently runs only on Linux, and he recommends external adapters for monitor mode.