Unlike Google, which crawls the Web looking for websites, Shodan navigates the Internet's back channels. It's a kind of "dark" Google, looking for the servers, webcams, printers, routers and all the other stuff that is connected to and makes up the Internet. (Shodan's site was slow to load Monday following the publication of this story.)
Shodan runs 24/7 and collects information on about 500 million connected devices and services each month.
It's stunning what can be found with a simple search on Shodan. Countless traffic lights,security cameras, home automation devices and heating systems are connected to the Internet and easy to spot.