Shodan is a search engine that lets the user find specific types of computers (web cams, routers, servers, etc.) connected to the internet using a variety of filters. Some have also described it as a search engine of service banners, which are meta-data the server sends back to the client. This can be information about the server software, what options the service supports, a welcome message or anything else that the client can find out before interacting with the server.
What Does it do?
Shodan collects data mostly on web servers (HTTP/HTTPS - port 80, 8080, 443, 8443), as well as FTP (port 21), SSH (port 22), Telnet (port 23), SNMP (port 161), SIP (port 5060) and Real Time Streaming Protocol (RTSP, port 554). The latter can be used to access webcams and their video stream.
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.
You can Register for a free account or - Pay 50$ for a premium account giving you access to all its features.
PS:Dorking with Shodan is AWESOME! Specially when you're conducting DDoS Attacks
