The sniffer cable is needed to connect a sniffer to an ethernet hub, but not transmit any data that may reveal the sniffer’s existence. This cable will return an inverted version of anything sent to the interface. The pinout for this cable is from the book Windows Forensics, by Chad Steel (ISBN 0-470-03862-4), but can also be found at dgonzalez.net, along with other useful pinouts for receive-only cables.
Orange White TD+ (pin 1)
Orange TD- (pin 2)
Green White RD+ (pin 3)
Green RD- (pin 6)
Hub Side:
Orange White is spliced into Green
Orange is spliced into Green White
Sniffer Side
Orange White is cut and sealed.
Orange is cut and sealed.