Nmap ("Network Mapper") is a free and open source (license) utility for network exploration or security auditing. Many systems and network administrators also find it useful for tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime.
Wireshark is a network protocol analyzer. It lets you capture and interactively browse the traffic running on a computer network.
Network Monitor 3.4 is a protocol analyzer. It allows you to capture network traffic, view and analyze it.Solar Winds IP Address Tracker
The ISC was created in 2001 following the successful detection, analysis, and widespread warning of the Li0n worm. Today, the ISC provides a free analysis and warning service to thousands of Internet users and organizations.
For DoD Only: The DoD version of NID (called JIDS) is available to DoD entities and DoD contractors at the DISA INFOSEC Tools Distribution site. If you are a DoD entity, download JIDS from that location.
Note: The tools described here are provided as-is and are for use at your own risk. Unless otherwise noted, no effort has been made to verify that the software is free from viruses, Trojan horses, or other forms of malicious programming. No effort has been made to verify that the software performs as its authors claim.