This is a good one, let me tell you! There can be so many issues setting up your box to actually get the tools working and i'm not even touching on that, but if you can get everything to work, you'll be cracking wireless networks like a pro in no time. Disclaimer: I'm not a pro.
Note: Make sure you can get your card into monitor mode (sometimes called raw monitor or rfmon). This is VERY important
A little theory first. WEP is a really crappy and old encryption techinque to secure a wireless connection. A 3-byte vector, called an Initalization Vector or IV, is prepended onto packets and its based on a pre-shared key that all the authenticated clients know… think of it as the network key you need to authenticate.
Well if its on (almost) every packet generated by the client or AP, then if we collect enough of them, like a few hundred thousand, we should be able to dramatically reduce the keyspace to check and brute force becomes a realistic proposition.
A couple of things will cause us some problems.
We're gonna need 3 or 4 shells open, we have 5 tools:
For a standard WEP hack we'll usally only need airodump, aircrack, and kismet (server and client). If we run into some problems we might have to use airreplay to fiddle about.
I'll leave you to config all these tools up, for the most part they should just be defaults with the exception of kismet.
First step is we need to find a netork to crack. Start up kismet and start sniffing for APs. Leave it on for a bit so that it can discover all the important information about the networks around. What we want from kismet is:
All this info isn't required but the more you have, the more options you have later to crack and sniff. We can get a lot of this from airodump as well but I find the channel is important.
Alright, we know what we wanna crack, so lets start capturing packets. You can use kismet to capture files but I prefer airodump because it keeps a running count of all the IVs I've captured and I can crack and airodump will automatically update aircrack with new IVs as it finds them.
Note: kimset can interfere with airodump so make sure you close it down before starting airodump.
Airodump is pretty straight forward with its command line looking something like this:
./airodump <interface> <output prefix> [channel] [IVs flag]
My wireless card is ath0, output prefix i'll use „lucid“, the channel we sniffed from kismet is 6, and IVs flag is 1 because we just want IVs. So we run:
./airodump ath0 lucid 6 1
Airodump will come up with a graph showing us all the APs and their relevant info, as well as client stations connected to any of the APs.
BSSID PWR Beacons # Data CH MB ENC ESSID 00:23:1F:55:04:BC 76 21995 213416 6 54. WEP hackme BSSID STATION PWR Packets Probes 00:23:1F:55:04:BC 00:12:5B:4C:23:27 112 8202 hackme 00:23:1F:55:04:BC 00:12:5B:DA:2F:6A 21 1721 hackme
The second line shows us some info about the AP as well as the number of beacons and data packets we've collected from the AP. The two last lines show us two authenticated clients. Where they are connected to and the packets they are sending. We won't use this client info in a straight theory hack but in practice we'll need this info to actively attack the AP.
This step may take a long time or could be very short. It depends how busy the AP is and how many IVs we are collecting. What we are doing is populating a file „lucid.ivs“ with all the IV important packet info. Next, we'll feed this to aircrack. To move onto the next step, we'll want at least 100,000 packets (under # Data in airodump) but probably more.
Ok, pretend you have enough IVs now to attempt a crack. Goto a new terminal (without stopping airodump - remember it'll autoupdate as new IVs are found) and we'll start aircrack. It looks something like this:
./aircrack [options] <input file>
There are a lot of options so you can look them up yourself, i'll be using common ones here that should get you a crack. Our input file is „lucid.ivs“, the options we will use are:
So our command will look like:
./aircrack -a 1 -b 00:23:1F:55:04:BC -n 128 lucid.ivs
and off it goes, resembling the picture from the top. Keep an eye on the Unique IV count as it should increase if airodump is still running. For all intents and purposes you are done. That'll pop open most old wireless routers with some traffic on them.
There are lots of problems that can come up that will make the above fail, or work very slowly.
WPA is an encryption algorithm that takes care of a lot of the vunerablities inherent in WEP. WEP is, by design, flawed. No matter how good or crappy, long or short, your WEP key is, it can be cracked. WPA is different. A WPA key can be made good enough to make cracking it unfeasible. WPA is also a little more cracker friendly. By capturing the right type of packets, you can do your cracking offline. This means you only have to be near the AP for a matter of seconds to get what you need. Advantages and disadvantages.
WPA basically comes in two flavours RADIUS or PSK. PSK is crackable, RADIUS is not so much.
PSK uses a user defined password to initialize the TKIP, temporal key integrity protocol. There is a password and the user is involved, for the most part that means it is flawed. The TKIP is not really crackable as it is a per-packet key but upon the initialization of the TKIP, like during an authentication, we get the password (well the PMK anyways). A robust dictionary attack will take care of a lot of consumer passwords.
Radius involves physical transferring of the key and encrypted channels blah blah blah, look it up to learn more about it but 90% of commerical APs do not support it, it is more of an enterprise solution then a consumer one.
The WPA handshake was designed to occur over insecure channels and in plaintext so the password is not actually sent across. There are some fancy dancy algorithms in the background that turn it into a primary master key, PMK, and the like but none of that really matters cause the PMK is enough to connect to the network.
The only step we need to do is capture a full authenication handshake from a real client and the AP. This can prove tricky without some packet injection, but if you are lucky to capture a full handshake, then you can leave and do the rest of the cracking at home.
We can force an authenication handshake by launching a Deauthentication Attack, but only if there is a real client already connected (you can tell in airodump). If there are no connected clients, you're outta luck.
Like for WEP, we want to know the channel the WPA is sitting on, but the airodump command is slightly different. We don't want just IVs so we don't specify an IV flag. This will produce „lucid.cap“ instead of „lucid.ivs“. Assume WPA is on channel 6 and wireless interface is ath0.
./airodump ath0 lucid 6
The most important part of brute forcing a WPA password is a good dictionary. Check out http://www.openwall.com/wordlists/ for a 'really' good one. It costs money, but its the biggest and best I've ever seen (40 Million words, no duplicates, one .txt file). There is also a free reduced version from the same site but i'm sure resourceful people can figure out where to get a good dictionary from.
When you have a good dictionary the crack is a simple brute force attack:
./aircrack -a 2 -b 00:23:1F:55:04:BC -w /path/to/wordlist
Either you'll get it or you won't… depends on the strength of the password and if a dictionary attack can crack it.
Aireplay is the fun part. You get to manipulate packets to trick the network into giving you what you want.
Attacks used to create more traffic on WEP networks to get more IVs.
ARP Replay is a classic way of getting more IV traffic from the AP. It is the turtle. Slow but steady and almost always works. We need the BSSID of the AP and the BSSID of an associated client. If there are no clients connected, it is possible to create one with another WEP attack explained below: Fake Authentication Attack.
With airodump listening, we attack:
./aireplay -3 -b <AP MAC Address> -h <Client MAC Address> ath0
Note: The -3 specifys the type of attack (3=ARP Replay).
This will continue to run, and airodump, listening fron another terminal, will pick up any reply IVs.
Interactive Packet Reply is quite a bit more advanced and requires capturing packets and constructing your own. It can prove more effective then simple ARP requests but I won't get into packet construction here.
A useful attack you might try is the re-send all data attack, basically you are asking the AP to re-send you everything. This only works if the AP re-encrypts the packets before sending them again (and therefore giving you a new IV). Some APs do, some don't.
aireplay -2 -b <AP MAC> -h <Client MAC> -n 100 -p 0841 -c FF:FF:FF:FF:FF:FF ath0
This attack won't generate any more traffic but it does create an associative client MAC Address useful for the above two attacks. Its definately not as good as having a real, connected client, but you gots to do what you gots to do.
This is done easiest with another machine because we need a new MAC address but if you can manually change your MAC then that'll work too. We'll call your new MAC address „Fake MAC“.
Now most APs need clients to reassociate every 30 seconds or so or they think they're disconnected. This is pretty arbitrary but I use it and it has worked but if your Fake MAC gets disconnected, reassociate quicker. We need both the essid and bssid and our Fake MAC.
./aireplay -1 30 -e '<ESSID>' -a <BSSID> -h <Fake MAC> ath0
If successful, you should see something like this:
23:47:29 Sending Authentication Request 23:47:29 Authentication successful 23:47:30 Sending Association Request 23:47:30 Association successful :-)
Awesome! Now you can use the above two attacks even though there were no clients connected in the first place! If it fails, there may be MAC Address Filtering on so if you really want to use this, you'll have to sniff around until a client provides you with a registered MAC to fake.
So far, the only way to really crack WPA is to force a re-authentication of a valid client. We need a real, actively connected client to break WPA. You might have to wait a while.
This is a simple and very effective attack. We just force the connected client to disconnect then we capture the re-connect and authentication, saves time so we don't have to wait for the client to do it themselves (a tad less „waiting outside in the car“ creepiness as well). With airodump running in another console, your attack will look something like this:
aireplay -0 5 -a <AP MAC> -c <Client MAC> ath0
After a few seconds the re-authentication should be complete and we can attempt to Dictionary Brute Force the PMK.
Well thats that. APs crack fairly often but sometimes there is just nothing you can do. Obviously you are not allowed to illegally crack other people's wireless connections, this is purely for penetration testing purposes and some fun.
— Bryan Rite 13:57, 24 Nov 2005 (PST)