Little Snitch - Little Snitch is a firewall application that monitors and controls outbound internet traffic.
TrafficMonitor - TrafficMonitor is a network monitoring suspension window software in Windows.
Radio Silence - Radio Silence is a network monitor and firewall for the macOS. The software stops apps from making network connections. The firewall runs in the background and does not require an open window.
NetBalancer - NetBalancer is a Windows application for local network traffic control and monitoring.
Hands Off! - Monitor your computer. Protect your privacy.
FreeMeter - Monitor network bandwidth (C#.NET 2k/XP+). Desktop and Systray graph.