Short for Radio Frequency Monitoring, RFMON is a passive method of WLAN discovery. It is a sniffing mode which allows the card to report drivers from the 802.11 layer. A client with a wireless card that is configured in RFMON mode will be able to capture all RF signals on the channels to which it is configured to listen. RFMON is a receive-only mode. While in RFMON mode, wireless clients are unable to transmit any frames; their cards are only able to receive, and therefore capture traffic.