Options
Project Sonar - by Rapid7
Take a look at the below, very cool stuff by Rapid7. They have developed a tool that scans the entire ipv4 space for research purposes and make the paper available. Some pretty interesting stuff on the paper, like finding out1/3rd of the spublic servers are still using telnet
https://sonar.labs.rapid7.com
https://sonar.labs.rapid7.com
