Step 2 - Set Card to Monitor Mode

As mentioned earlier, the WLAN card you use must be capable of being put into "monitor" mode. This means that it can capture all packets it detects and not just the ones intended for its MAC address. This is similar to an Ethernet card being put into promiscuous mode, which is required for packet sniffers / analyzers such as Wireshark (Ethereal) or OmniPeek Personal.

We'll use the airmon-ng script to put the card into monitor mode. First just type:

airmon-ng

to check the adapter status. Then:

airmon-ng stop ath0

to stop the interface. Then type:

airmon-ng start wifi0

to restart the adapter in monitor mode.

Note that you use wifi0, not ath0 in the start command. This has to do with the way that the Atheros madwifi driver works. The sequence and resulting output from each command line are shown in Figure 2.

Figure 2: airmon-ng command output

You can check that monitor mode is enabled by entering the iwconfig command. Figure 3 shows the result, which confirms that the adapter is in monitor mode and ready to go.

Figure 3: Atheros adapter in monitor mode