Nmap is now one of the core tools used by network administrators to map their networks. Nmap, short for Network Mapper, is a free, open-source tool for vulnerability scanning and network discovery. Nmap is a tool that can be used to discover services running on Internet connected systems. Detect the vulnerability and security holes (Nmap scripts). Nmap uses raw IP packets in novel ways to determine what hosts are available on the network, what. Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool.