FastNetMon vs Nfsen

FastNetMon is an open-source network monitoring tool that analyzes traffic patterns to detect network outages, DDoS attacks, suspicious access to critical systems, and other issues. It works by analyzing netflow, sflow, and mirroring ports on switches.

Nfsen is an open source Netflow sensor for network traffic monitoring. It provides extensive visualization tools and options for analyzing network flows collected by Netflow enabled routers and switches.