Nmap vs tcpdump

Nmap is a free, open-source utility for discovering networks and auditing security. It uses raw IP packets to identify available hosts, services and versions, operating systems, and packet filters or firewalls. Scanning options include TCP and UDP ports, OS and version detection, and ping sweeps. Network administrators can use it to inventory systems, plan service upgrades, and monitor host or service uptime. The Nmap Scripting Engine runs bundled or user-written scripts in parallel for networking tasks such as discovery and vulnerability checks. The suite also includes Zenmap, a graphical interface and results viewer; Ncat for data transfer and debugging; Ndiff for comparing scan results; and Nping for packet generation and response analysis. Most port-scan types require privileged access to send and receive raw packets, although unprivileged users can run connect and FTP bounce scans. Nmap is not a comprehensive vulnerability scanner. End-user use is free, but redistribution in commercial products requires an OEM license. Quarterly OEM licenses start at $9,980.00 per 3 months for eligible small or startup companies.

tcpdump is a network monitoring and data acquisition tool that captures traffic through libpcap, an interface for user-level packet capture. It provides command-line tools and PCAP support, and the project lists systems including AIX, BSD variants, GNU/Linux, macOS, Solaris, QNX, and Windows. It is free, with source code available through a public Git repository and native packages or ports on many systems.

Building requires libpcap and a C99-compliant compiler. Windows builds also require WinPcap or Npcap and Visual Studio with CMake. The license permits redistribution and use in source and binary forms under its conditions. Capture permissions depend on the operating system and its configuration; the project cautions that permitted users may capture network traffic, including passwords. Native packages may lag a few versions, while a newer snapshot can be compiled from source. The project lists Linux, macOS, and Windows among its platforms.