netsniff-ng is is a free, performant Linux network analyzer and networking toolkit.
The gain of performance is reached by zero-copy mechanisms, so that the kernel does not need to copy packets from kernelspace to userspace and vice versa.
netsniff-ng consists of much more than only a network analyzer. Next to the zero-copy sniffer itself, further tools like trafgen, a powerful zero-copy network packet generator, or ifpps, a tool that provides top-like kernel networking statistics, and curvetun, a lightweight curve25519-based multiuser IP tunnel, are being shipped.
These details are provided for information only. No information here is legal advice and should not be used as such.