Inspiration can come from many places. When [Veronica Valeros] and [Sebastian Garcia] from the MatesLab Hackerspace in Argentina learned that it took [Ai Weiwei] four years to discover his home had been bugged, they decided to have a closer look into some standard audio surveillance devices. Feeling there’s a shortage of research on the subject inside the community, they took matters in their own hands, and presented the outcome in their Spy vs. Spy: A modern study of microphone bugs operation and detection talk at 34C3. You can find the slides here, and their white paper here.
Focusing their research primarily on FM radio transmitter devices, [Veronica] and [Sebastian] start off with some historical examples, and the development of such devices — nowadays available off-the-shelf for little money. While these devices may be shrugged off as a relic of Soviet era spy fiction and tools of analog times, the easy availability and usage still keeps them relevant today. They conclude their research with a game of Hide and Seek as real life experiment, using regular store-bought transmitters.
An undertaking like this would not be complete without the RTL-SDR dongle, so [Sebastian] developed the Salamandra Spy Microphone Detection Tool as alternative for ready-made detection devices. Using the dongle’s power levels, Salamandra detects and locates the presence of potential transmitters, keeping track of all findings. If you’re interested in some of the earliest and most technologically fascinating covert listening devices, there is no better example than Theremin’s bug.
At least that’s how [Antibore] handled the situation, and the results are pretty good. He designed his build around an old Raspberry Pi 2 that was hanging around. That required a WiFi adapter, and since he wanted video and audio he needed a camera and mic. The first USB mic had a nice compact design but didn’t perform well, so a gutted gooseneck mic soldered right to the USB connector joined the design spec. A camera module, cell-phone quick charge battery bank, and a 3D printed case round out the BOM. A knitted cozy to keep it looking warm and fuzzy was provided by the mother-to-be — although we think it 
Another problem is that for stereo recording you need two and because they are quiet, they tend to pick up handling noise so you probably need to mount them on tripods. That’s all too much to carry around, especially on a hike. So [Matt] 
