sniffer

Sniffer From Hackepedia

Packet sniffers do exactly what the name implies, they allow you to watch the packets that are touching your host. For good they extremely helpful in debugging problems with networks. They can also be used for several malicious purposes including spying on people and harvesting passwords.

You can use a packet sniffer on any network interface. ifconfig will give you a list of your network interfaces on UBOs.