Active Attack

Using the information we gathered with Kismet during the recon step, we can target associated clients of a certain AP with forged deauthentication packets, which should cause the client to disassociate from the AP. We then listen for the reassociation and subsequent authentication. This is a little trickier and also detectable, since we're sending out packets. But it's much quicker than waiting for a genuine association (in most cases).

After identifying our target AP with associated clients, we need to set up the wireless hardware for packet injection. The aircrack suite has a little bash script to do just that.

First bring down the managed VAP (Virtual Access Point) with:

airmon-ng stop ath0

Figure 2: Bringing down the managed interface

Next, start up a VAP in "Monitor" mode:

airmon-ng start wifi0

Figure 3: Creating a monitor mode interface

Now we need to simultaneously deauthenticate a client and capture the resulting reauthentication. Open up two terminal windows. Start airodump-ng in one terminal:

General Form:

airodump-ng -w capture_file_prefix --channel channel_number interface

Example:

airodump-ng -w cap --channel 6 ath0

Figure 4: airodump-ng, up and running

Note:
You can check which interface is in monitor mode by using iwconfig.

Next, run the deathentication attack with aireplay-ng in the other terminal:

General Form:

aireplay-ng --deauth 1 -a MAC_of_AP -c MAC_of_client interface

Example:

aireplay-ng --deauth 1 -a 00:18:E7:02:4C:E6 -c 00:13:CE:21:54:14 ath0

Figure 5: A successfully sent deathentication packet

If all goes well, the client should be deauthenticated from the AP and will usually reauthenticate. I like to keep the number of deauthentication packets sent to a minimum (one, in this case). This helps keep you under the radar, since programs like Kismet can detect deauthentication floods.

If the deauthentication was successful, airodump-ng displays a notification of the captured reauthentication event (boxed in red in Figure 6).

Figure 6: Successful WPA handshake capture

Tags: Hacking, How To, WiFi, WPA,

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