Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
SIREN.io - Siren is an investigative intelligence platform.
Angry IP Scanner - Open-source and cross-platform network scanner designed to be fast and simple to use
DataWalk - DataWalk is a software platform to connect numerous large data sets, both external and internal, into a single repository for fast visual analysis.
Zenmap - Zenmap is the official cross-platform GUI for the Nmap Security Scanner.
Sentinel Visualizer - Link Analysis, Data Visualization, Geospatial Mapping, and Social Network Analysis (SNA) with Sentinel Visualizer