From Motherboard:

Motherboard’s investigation shows just how exposed mobile networks and the data they generate are, leaving them open to surveillance by ordinary citizens, stalkers, and criminals, and comes as media and policy makers are paying more attention than ever to how location and other sensitive data is collected and sold. The investigation also shows that a wide variety of companies can access cell phone location data, and that the information trickles down from cell phone providers to a wide array of smaller players, who don’t necessarily have the correct safeguards in place to protect that data.