promiscuous mode

Definition of promiscuous mode in The Network Encyclopedia.

What is Promiscuous Mode?

A mode of operation of a network interface card (NIC) in which the NIC accepts all frames on the wire, including those not specifically directed to it. A NIC operating in promiscuous mode reads every frame it receives, whether the frames are broadcast, multicast, or directed.

In some networks, this can be a security problem because nodes that act “promiscuously” can be configured not only to read frames but also to store them and even retransmit them.

Sensitive information can thus be intercepted on the network and retransmitted to remote stations. This problem can occur in both Ethernet and Token Ring networks when NICs are configured to act promiscuously.


Network driver interface specification (NDIS), as of version 4, supports a capturing mode called local only, which uses fewer CPU resources than promiscuous mode but supports capturing of all frames for Microsoft Network Monitor.