netsniff-ng is described as 'Free, performant Linux networking toolkit. The gain of performance is reached by zero-copy mechanisms, so that on packet reception and transmission the kernel does not need to copy packets from kernel space to user space and vice versa' and is an app in the network & admin category. There are more than 10 alternatives to netsniff-ng for a variety of platforms, including Windows, Mac, Linux, Android and iPhone apps. The best netsniff-ng alternative is inSSIDer. It's not free, so if you're looking for a free alternative, you could try Aircrack-ng or Homedale. Other great apps like netsniff-ng are NetSpot, Vistumbler, NetStumbler and Kismet.