You need to be connected to the network you are sniffing on in order for ettercap to work. In other words you want your interface to be in managed mode and properly associated with your AP before you start ettercap. If you want to sniff the traffic without having to connect to the AP you will have to capture all appropriate packets flying by and then replay them using tcpreplay on the loopback interface to dissect the URL information with urlsnarf.



