This tutorial walks you through cracking WPA/WPA2 networks which use pre-shared keys. I recommend you do some background reading to better understand what WPA/WPA2 is. The Wiki links page has a WPA/WPA2 section. The best document describing WPA is Wi-Fi Security - WEP, WPA and WPA2. This is the link to download the PDF directly. The WPA Packet Capture Explained tutorial is a companion to this tutorial.
WPA/WPA2 supports many types of authentication beyond pre-shared keys. aircrack-ng can ONLY crack pre-shared keys. So make sure airodump-ng shows the network as having the authentication type of PSK, otherwise, don't bother trying to crack it.
There is another important difference between cracking WPA/WPA2 and WEP. This is the approach used to crack the WPA/WPA2 pre-shared key. Unlike WEP, where statistical methods can be used to speed up the cracking process, only plain brute force techniques can be used against WPA/WPA2. That is, because the key is not static, so collecting IVs like when cracking WEP encryption, does not speed up the attack. The only thing that does give the information to start an attack is the handshake between client and AP. Handshaking is done when the client connects to the network.Although not absolutely true, for the purposes of this tutorial, consider it true. Since the pre-shared key can be from 8 to 63 characters in length, it effectively becomes impossible to crack the pre-shared key.
The only time you can crack the pre-shared key is if it is a dictionary word or relatively short in length. Conversely, if you want to have an unbreakable wireless network at home, use WPA/WPA2 and a 63 character password composed of random characters including special symbols.
The impact of having to use a brute force approach is substantial. Because it is very compute intensive, a computer can only test 50 to 300 possible keys per second depending on the computer CPU. It can take hours, if not days, to crunch through a large dictionary. If you are thinking about generating your own password list to cover all the permutations and combinations of characters and special symbols, check out this brute force time calculator first. You will be very surprised at how much time is required.
IMPORTANT This means that the passphrase must be contained in the dictionary you are using to break WPA/WPA2. If it is not in the dictionary then aircrack-ng will be unable to determine the key.
It is recommended that you experiment with your home wireless access point to get familiar with these ideas and techniques. If you do not own a particular access point, please remember to get permission from the owner prior to playing with it.
In the response above, you can see that ath0 is in monitor mode, on the 2.452GHz frequency which is channel 9 and the Access Point shows the MAC address of your wireless card. Only the madwifi-ng drivers show the card MAC address in the AP field, other drivers do not. So everything is good. It is important to confirm all this information prior to proceeding, otherwise the following steps will not work properly.
Notice that airmon-ng enabled monitor-mode on mon0. So, the correct interface name to use in later parts of the tutorial is mon0. Wlan0 is still in regular (managed) mode, and can be used as usual, provided that the AP that wlan0 is connected to is on the same channel as the AP you are attacking, and you are not performing any channel-hopping.
Here, mon0 is seen as being in monitor mode, on channel 9 (2.452GHz). Unlike madwifi-ng, the monitor interface has no Access Point field at all. Also notice that wlan0 is still present, and in managed mode - this is normal. Because both interfaces share a common radio, they must always be tuned to the same channel - changing the channel on one interface also changes channel on the other one.
This step is optional. If you are patient, you can wait until airodump-ng captures a handshake when one or more clients connect to the AP. You only perform this step if you opted to actively speed up the process. The other constraint is that there must be a wireless client currently associated with the AP. If there is no wireless client currently associated with the AP, then you have to be patient and wait for one to connect to the AP so that a handshake can be captured. Needless to say, if a wireless client shows up later and airodump-ng did not capture the handshake, you can backtrack and perform this step.
This step sends a message to the wireless client saying that that it is no longer associated with the AP. The wireless client will then hopefully reauthenticate with the AP. The reauthentication is what generates the 4-way authentication handshake we are interested in collecting. This is what we use to break the WPA/WPA2 pre-shared key.
The purpose of this step is to actually crack the WPA/WPA2 pre-shared key. To do this, you need a dictionary of words as input. Basically, aircrack-ng takes each word and tests to see if this is in fact the pre-shared key.
When this happens you either have to redo step 3 (deauthenticating the wireless client) or wait longer if you are using the passive approach. When using the passive approach, you have to wait until a wireless client authenticates to the AP.
Unfortunately, sometimes you need to experiment a bit to get your card to properly capture the four-way handshake. The point is, if you don't get it the first time, have patience and experiment a bit. It can be done!
In an ideal world, you should use a wireless device dedicated to capturing the packets. This is because some drivers such as the RTL8187L driver do not capture packets the card itself sends. Also, always use the driver versions specified on the wiki. This is because some older versions of the drivers such as the RT73 driver did not capture client packets.
To dig deep into the packet analysis, you must start airodump-ng without a BSSID filter and specify the capture of the full packet, not just IVs. Needless to say, it must be locked to the AP channel. The reason for eliminating the BSSID filter is to ensure all packets including acknowledgments are captured. With a BSSID filter, certain packets are dropped from the capture.
When it comes to analyzing packet captures, it is impossible to provide detailed instructions. I have touched on some techniques and areas to look at. This is an area which requires effort to build your skills on both WPA/WPA2 plus how to use Wireshark.
Idea and initial work: ASPj
Additions by: a number of good souls
Last updated: Nov 21, 2018
This tutorial will give you the basics to get started using the aircrack-ng suite. It is impossible to provide every piece of information you need and cover every scenario. So be prepared to do some homework and research on your own. The Forum and the Wiki have lots of supplementary tutorials and information.
The first step in getting aircrack-ng working properly on your Linux system is patching and installing the proper driver for your wireless card. Many cards work with multiple drivers, some of which provide the necessary features for using aircrack-ng, and some of which do not.
Needless to say, you need a wireless card which is compatible with the aircrack-ng suite. This is hardware which is fully compatible and can inject packets. A compatible wireless card can be used to crack a wireless access point in under an hour.
To determine to which category your card belongs to, see hardware compatibility page. Read Tutorial: Is My Wireless Card Compatible? if you don't know where to look in this table. It still does not hurt to read this tutorial to build your knowledge and confirm your card attributes.
First, you need to know which chipset is used in your wireless card and which driver you need for it. You will have determined this using the information in the previous paragraph. The drivers section will tell you which drivers you need.
The following chapter is very important, if something doesn't work as expected. Knowing what all is about helps you find the problem or helps you at least to describe it so someone else who can help you. This is a little bit scientific and maybe you feel like skipping it. However, a little knowledge is necessary to crack wireless networks and because it is a little more than just typing one command and letting aircrack do the rest.
This is a short introduction into managed networks, these ones working with Access Points (AP). Every AP sends out about 10 so called beacon frames a second. These packets contain the following information:
Every AP has a unique MAC address (48 bit, 6 pair of hexadecimal numbers). It looks like 00:01:23:4A:BC:DE. Every network hardware device has such an address and network devices communicate with each other by using this MAC address. So its basically like a unique name. MAC addresses are unique, no two network devices in the world have the same MAC address.
If you want to connect to a wireless network, there are some possibilities. In most cases, Open System Authentication is used. (Optional: If you want to learn more about authentication, check this out.)
airodump-ng hops from channel to channel and shows all access points it can receive beacons from. Channels 1 to 14 are used for 802.11b and g (in US, they only are allowed to use 1 to 11; 1 to 13 in Europe with some special cases; 1-14 in Japan). 802.11a is in the 5GHz and availability in different countries is more fragmented than on 2.4GHz. In general, known channels starts at 36 (32 in some countries) to 64 (68 in some countries) and 96 to 165. Wikipedia has more details on channel availability. The Linux Central Regulatory Domain Agent takes care of allowing/forbidding transmissions on the different channels for your country; however, it needs to be set appropriately.
Now you should look out for a target network. It should have a client connected because cracking networks without a client is an advanced topic (See How to crack WEP with no clients). It should use WEP encryption and have a high signal strength. Maybe you can re-position your antenna to get a better signal. Often a few centimeters make a big difference in signal strength.
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