iftop is described as 'does for network usage what top(1) does for CPU usage. It listens to network traffic on a named interface and displays a table of current bandwidth usage by pairs of hosts' and is an app in the Network & Admin category. There are five alternatives to iftop for a variety of platforms, including Linux, BSD, Solaris, Xfce and Mac. The best alternative is Nethogs, which is both free and Open Source. Other great apps like iftop are nload (Free, Open Source), ntop (Free, Open Source), Bandwhich (Free, Open Source) and IPtraf-ng (Free, Open Source).