Powerfull low-level network library which allows you to send modified/spoofed packets over the network. USI++ runs on Linux and FreeBSD systems and supports 10MBit, 100MBit and PPP-devices. v1.63 comes with some bugfixes; it now works properly on FreeBSD. USI++ requires libpcap. All linux and BSD distributions should include libpcap.
You can download it from the following link: https://packetstormsecurity.com/files/download/11128/usi%2B%2B.tar.gz
Source: https://packetstormsecurity.com/files/11128/usi-.tar.gz.html