Nmap is a de facto tool for information gathering, and the variety of tasks that can be done
with the Nmap Scripting Engine is simply remarkable. The popular service "ShodanHQ"
(http://shodanhq.com) offers a database of HTTP banners, which is useful for analyzing
the impact of vulnerabilities. Its users can find out the number of devices that are online, by
country, which are identified by their service banners. ShodanHQ uses its own built-in house
tools to gather its data, but Nmap is also perfect for this task.