Nmap

Nmap, short for Network Mapper, is the tool most of this category is measured against and the one least like the rest of it. It is a free and open-source utility for network discovery and security auditing, run from the command line rather than a dashboard, and it produces scan results rather than maintained topology diagrams. Buyers wanting continuously updated documentation should look at the commercial tools here; those wanting to know precisely what is on a network right now start with Nmap.

It is a suite rather than a single binary. Zenmap provides a graphical front end, Ncat handles data transfer, redirection and debugging, Ndiff compares scan results between runs to reveal what changed, and Nping generates packets and analyses responses. On Windows it depends on the Npcap packet capture library. The Nmap Scripting Engine extends scanning far beyond port discovery into service and vulnerability checks. The current release is Nmap 7.99, and the project has been developed continuously since 1997. It may be modified and redistributed under the terms of its licence.