promiscuous mode
termnetworkingsecurity
A network interface setting that accepts every frame on the wire, not just those addressed to it.
Normally a NIC ignores frames whose destination MAC is not its own; promiscuous mode disables that filter so a capture tool can see the whole segment, which is what Wireshark and tcpdump rely on. On a shared medium like old hubbed Ethernet or open wireless (where the equivalent is monitor mode) that meant seeing everyone's traffic, so switched networks and a SPAN/mirror port became the sanctioned way to feed a sensor. The setting is neutral, and the same capability serves both the troubleshooter and the eavesdropper.
Also known as: promisc, monitor mode