WinPcap, a free Windows port of the UNIX libpcap packet-capture library, is also necessary to run Nmap, WinDump, and Snort on the Windows platform. Nmap is a great free port scanner, and WinDump is the Windows version of tcpdump, a command-line protocol analyzer similar to Tethereal. Snort is a popular open-source Intrusion Detection System (IDS). You can download Nmap from, WinDump from, and Snort from Be aware that the current version of WinPcap can't capture 802.11 wireless packets in promiscuous mode; hence, Ethereal can display only the packets going to and from your own wireless adapter card.