Tony's Ethernet Tap
Tony ( garfunct "at" g-mail .com ) submitted the following information and images on making an Ethernet wire tap. This could be a good alternative if you have two NICs and don't want to use bridging or ARP poisoning while sniffing a line you have access to.
I have been working my way through your videos. Your voice over ip sniff video has prompted me to pull out a small device I put together.
Thought you and or your viewers might appreciate it.
The middle port is regular ethernet hook up, if you are quick this can be slipped in and tcp will just resend error packages anyway so chances are users barely notice!
Voip is somewhat different obv.
You need 2 cards in the ids box (the 2 outside jacks only have receive wires hooked up windows will give connection error but not linux)
You can sniff on the ports data in both directions and have no worries someone will spot you on the network as you can only receive etc....