netsniff-ng is is a free, performant Linux network sniffer for packet inspection. The gain of performance is reached by ‘zero-copy’ mechanisms, so that the kernel does not need to copy packets from kernelspace to userspace. For this purpose netsniff-ng is libpcap independent, but nevertheless supports the pcap file format for capturing, replaying and performing offline-analysis of pcap dumps. netsniff-ng can be used for protocol analysis, reverse engineering and network debugging.
You can download it from the following link: https://packetstormsecurity.com/files/download/126394/netsniff-ng-0.5.8.tar.gz
Source: https://packetstormsecurity.com/files/126394/Netsniff-NG-High-Performance-Sniffer-0.5.8.html