" I felt a stir of hope. Computers and smartphones left a number trail as distinct as tracks in the snow each time they touched the Internet. One of these numbers was assigned by providers but one was hardwired into the device. From the instant a person signed on, their computer’s numerical path was logged and recorded by Internet service providers, networks, wireless hotspots, servers, and routers, forever linking the time, location, and path of service to your specific machine. Surf the Net, check your email, chat with a friend—each new router and service provider recorded and stored your numbers. The geolocation of a computer could be found by back-tracing this trail of numbers. Finding an approximate location was relatively easy. The spooks Jon knew could probably back-trace to a specific sign-on address, identify a specific machine, and pull the name of the person who bought it from the manufacturer. I "
― Robert Crais , The Promise (Elvis Cole, #16; Joe Pike, #5; Scott James & Maggie, #2)