HackerOne - HackerOne provides a platform designed to streamline vulnerability coordination and bug bounty program by enlisting hackers.
Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
Intruder - Intruder is a security monitoring platform for internet-facing systems.
Angry IP Scanner - Open-source and cross-platform network scanner designed to be fast and simple to use
Forcepoint Web Security Suite - Internet Security
Advanced IP Scanner - Advanced IP Scanner shows all network devices, gives you access to shared folders, and can even remotely switch computers off. Download it Free.