ZMap is a fast network scanner designed for Internet-wide network surveys. On a
typical desktop computer with a gigabit Ethernet connection, ZMap is capable
scanning the entire public IPv4 address space in under 45 minutes.
While previous network tools have been designed to scan small network segments,
ZMap is specifically architected to scan the entire address space. It is built
in a modular manner in order to allow incorporation with other network survey
tools. ZMap operates on GNU/Linux and supports TCP SYN and ICMP echo request
scanning out of the box.
Download and more info: https://zmap.io