Backtrack logo (Photo credit: Wikipedia)
Nowadays, there are wireless hotspots everywhere! You can get internet access with a wireless enabled laptop almost everywhere you go. In this page I will discuss ways a hacker goes about getting into secure wireless networks and things he can do once he is inside.
Scanning for Wireless Networks
For this section and the following, you will need to have a wireless card/adapter. The hacker starts by scanning for wireless networks near him. The Windows tool we will use in this section is called NetStumbler. Also by the time you receive this eBook MacStumbler may already be released for those of you using a Mac. Some other similar programs are:
• Kismet for Windows and Linux.
• KisMac for the Mac.
1. Download and install NetStumbler.
2. Run it. It automatically starts to scan for wireless access points.
3. Once it is completed, you should see a list of all the wireless access points around you.
4. If you click on the MAC address of one of the discovered wireless networks under channels, you will see a graph that shows the wireless network’s signal strength. The more green and the less spaces, the better the signal.
5. As you can see NetStumbler provides a lot more than just the name (SSID) of the wireless network. It provides the MAC address, Channel number, encryption type, and a bunch more. All of these come in use when a hacker decides he wants to get in the secured network by cracking the encryption. The most common types of encryption are:
• WEP (Wired Equivalent Privacy) – WEP isn’t considered safe anymore. Many flaws have been discovered that allow a hacker to crack a WEP key easily.
• WAP (Wireless Application Protocol) – WAP is the currently the most secure and best option to secure your wireless network. It’s not as easily cracked as WEP because the only way to retrieve a WAP key is to use a brute-force or dictionary attack. If your key is secure enough, a dictionary attack won’t work and it could take decades to crack it if you brute-force it. This is why most hackers don’t even bother.
In this section we will use be using the Live Linux distribution called BackTrack to crack WEP. Backtrack comes with a huge list of preloaded software for this very purpose. Before we begin, there are a couple requirements:
1. You need a computer with a compatible wireless adapter.
2. Download Backtrack and create a Live CD.
The tools we will be using on Backtrack are:
• Kismet – a wireless network detector
• airodump – captures packets from a wireless router
• aireplay – forges ARP requests
• aircrack – decrypts the WEP keys
1. First we will find a wireless access point along with its bssid, essid and channel number. To do this we will run kismet by opening up the terminal and typing in kismet. It may ask you for the appropriate adapter which in my case is ath0. You can see your device’s name by typing in the command iwconfig.
2. To be able to do some of the later things, your wireless adapter must be put into monitor mode. Kismet automatically does this and as long as you keep it open, your wireless adapter will stay in monitor mode.
3. In kismet you will see the flags Y/N/0. Each one stands for a different type of encryption. In our case we will be looking for access points with the WEP encryption. Y=WEP N=OPEN 0=OTHER(usually WAP).
4. Once you find an access point, open a text document and paste in the networks broadcast name (essid), its mac address (bssid) and its channel number. To get the above information, use the arrow keys to select an access point and hit <ENTER> to get more information about it.
5. The next step is to start collecting data from the access point with airodump. Open up a new terminal and start airodump by typing in the command:
airodump-ng -c [channel#] -w [filename] --bssid [bssid] [device]
In the above command airodump-ng starts the program, the channel of your access point goes after -c , the file you wish to output the data goes after -w , and the MAC address of the access point goes after --bssid. The command ends with the device name. Make sure to leave out the brackets.
6. Leave the above running and open another terminal. Next we will generate some fake packets to the target access point so that the speed of the data output will increase. Put in the following command:
aireplay-ng -1 0 -a [bssid] -h 00:11:22:33:44:55:66 -e [essid] [device]
In the above command we are using the airplay-ng program. The -1 tells the program the specific attack we wish to use which in this case is fake authentication with the access point. The 0 cites the delay between attacks, -a is the MAC address of the target access point, -h is your wireless adapters MAC address, -e is the name (essid) of the target access point, and the command ends with the your wireless adapters device name.
7. Now, we will force the target access point to send out a huge amount of packets that we will be able to take advantage of by using them to attempt to crack the WEP key. Once the following command is executed, check your airodump-ng terminal and you should see the ARP packet count to start to increase. The command is:
aireplay-ng -3 -b [bssid] -h 00:11:22:33:44:5:66 [device]
In this command, the -3 tells the program the specific type of attack which in this case is packet injection, -b is the MAC address of the target access point, -h is your wireless adapters MAC address, and the wireless adapter device name goes at the end.
8. Once you have collected around 50k-500k packets, you may begin the attempt to break the WEP key. The command to begin the cracking process is:
aircrack-ng -a 1 -b [bssid] -n 128 [filename].ivs
In this command the -a 1 forces the program into the WEP attack mode, the -b is the targets MAC address, and the -n 128 tells the program the WEP key length. If you don’t know the -n , then leave it out. This should crack the WEP key within seconds. The more packets you capture, the bigger chance you have of cracking the WEP key.
With all the different computers and network adapters out there, you may come across a error occasionally. If you get stuck, remember, Google is your friend! Search for an answer and I guarantee you that 99% of the time you will find a solution.
I will be using the program Wireshark do demonstrate packet sniffing. Packet sniffing is the act of capturing packets going through a network. With a packet sniffer, once a hacker gains access to wireless network he could intercept private information going through a network such as: usernames, passwords, IM conversations, and e-mails. Let’s show you an example.
1. Download and install Wireshark .
2. Launch it and click on the option to list the available capture interfaces as shown below.
3. Next choose the target to begin to capture their packets and click on start.
4. If you don’t know which one to choose, wait a little bit and the one that accumulates the most packets is your best choice. Many captured packets shows that the user is currently active.
5. Now to show you an example of how Wireshark can be used I will start up Windows Live and send a message. As you will see in the image below, my whole conversation will be captured. To filter out all the useless data and to only display the Windows Live related packets type in “msnms” in the filter bar.
6. As you can see, my message is displayed at the bottom. If I continue down the list I can see the whole conversation. Usernames and passwords are captured the same way, and if they aren’t encrypted, you can see them in plain text.
Some other useful sniffing programs to learn:
There are a few countermeasures you could follow to keep your wireless network safe from hackers.
1. Change your routers default password and make sure you have WAP encryption enabled. If your router doesn’t have a WAP option, use WEP. It is better than nothing.
2. Use a long secure password for your router. Include numbers, lowercase letters, uppercase letters and other symbols. The more obscure the better.
3. Make sure your router has the option to not broadcast your SSID enabled. This will prevent some programs like Net Stumbler from locating your wireless network.
4. Use MAC filtering on your router. Every wireless card and wireless adapter has a MAC address. By choosing to allow only your MAC addresses onto the network, you can keep a lot of attackers out.
5. To prevent packet sniffing attacks from affecting you, make sure the important sites you use, like banks, use SSL (Secure Socket Layer) encryption. You can tell if the site has SSL enabled if the URL begins with https:// instead of http:/.
6. In cafés or other hotspots where internet is free, packet sniffing is very common. To avoid being affected use a VPN (Virtual Private Network) service to encrypt the data you send across the internet.
Wireless Network Hacks & Mods for Dummies
359 pages | Publisher: For Dummies | English | ISBN-10: 0764595830 | PDF
Connect the old, the new, the practical, and the fun!
Play multiplayer games, set up home surveillance, or take your network outside
Now that you've got a wireless network going, you're getting the urge to see what else it can do, right? Hook up with this book and find simple, fun ways to expand its possibilities. Add your home entertainment gear, beef up speed and performance, discover wireless on the go, and get more out of your network!
Discover how to:
* Extend broadband throughout your home
* Protect your network from snoops
* Boost cellular signals
* Set up a wireless hot spot
* Take wireless to your car
* Make calls with your wireless network and VoIP