4G8 (Forge Gate) allows you to capture traffic from a third party in a switched environment at the expense of a slight increase in latency to that third party host. Utilizing ARP cache poisoning, packet capture and packet reconstruction techniques, 4G8 works with nearly all TCP, ICMP and UDP IPv4 traffic flows.

To run 4G8 you need to obtain the IP and MAC of the gateway, as well as the IP and MAC address of the target, both available by simply looking at the ARP table.

4G8 requires libnet 1.1 or greater as well as libpcap. It has been successfully compiled and tested to run on FreeBSD, NetBSD, OpenBSD and Linux.

Additional Information:
The tool can be downloaded from: http://forgate.sourceforge.net/downloads/4g8-0.9b.tgz

The information has been provided by Darren Bound through the securiteam mailing list.