GPS tracking device found on an activist's car
Very few companies produce GPS chips. Most devices that include GPS capability do not bother to reinvent the wheel, but instead elect to integrate an existing GPS processing chip. It's unlikely the GPS module is integrated with the processor core of this thing. Since it is likely separate, it would be fun to probe the PCB with a logic analyzer to see if there are any exposed serial (or possibly I2C, SPI) traces relaying the NMEA sentences[1] from the GPS module to the processor. If so, false locations could presented by severing the traces and soldering on a synthetic serial (or I2C, SPI) feed at the right logic level (probably 3.3V), from a microcontroller or computer. The hacked feed could even read a real-time clock to "play back" a stored path of locations every day. Attaching an external data feed is likely as simple as dragging a box cutter over the right traces (data, ground) to disrupt them, and then soldering on some 30 gauge wire to the same traces (after sanding off the soldermask and silkscreen). Since most GPS modules output constantly without any control lines, so there may not even be a control scheme to reverse engineer.<p>Note to those designing trackers: if you want to make it difficult, use a board with internal layers and keep the GPS nets on the interior of the board. Doesn't make splicing impossible[2], but it would up the difficulty.<p>1. <a href="http://aprs.gids.nl/nmea/" rel="nofollow">http://aprs.gids.nl/nmea/</a>
2. <a href="http://www.circuitrework.com/guides/4-2-6.shtml" rel="nofollow">http://www.circuitrework.com/guides/4-2-6.shtml</a>