How to Hack Wi-Fi: Getting Started with Terms and Technologies

I can hear you all groan, but you need to know the basics before you get into more advanced hacking. Then hopefully, developing your own hacks.

Afterward, the following guides will cover wardriving, DOS attacks, password hacking (WEP, WPA, WPA2, WPS, and WPA-enterprise), rogue APs, evil twins, Wi-Fi MitM, and Wi-Fi snooping. Lastly, we'll examine how to hack Bluetooth (yes, I know, technically it's not Wi-Fi, but I think you'll find it interesting).

So, come along for this frequent and amplified ride of Wi-Fi hacking!

Step 1: Terminology

To really understand how to hack Wi-Fi, we need to dispense with basic terms and technology. First, let's address some terminology.

To begin, the access point that sends out the radio frequency (RF) signal is known as the AP. These APs are capable of sending out signals (between 2.4 and 5 Ghz) that comply with a number of different standards. These standards are known as 802.11a, 802.11b, 802.11g, and 802.11n. In the very near future, we'll see a new standard that's tentatively named 802.11ac.

The table below summarizes the key features of these Wi-Fi standards.

These standards are generally backwardly compatible, so that a wireless n adapter will also be able to pick up g and b signals. We will focus upon the most widely used of these standards— b, g, and n.

Step 2: Security Technology

From the perspective of the hacker, wireless security technologies are among the most pertinent features. Multiple security technologies have been deployed in Wi-Fi to make an inherently insecure technology secure. Our attack approach will depend upon which of these security technologies is being deployed.

So, let's take a quick look at them here.

WEP

WEP, or wired equivalent privacy, was the first wireless security scheme employed. As it name implies, it was designed to provide security to the end-user that was essentially equivalent to the privacy that was enjoyed in a wired environment. Unfortunately, it failed miserably.

For a number of reasons, WEP is extraordinarily easy to crack because of a flawed implementation of the RC4 encryption algorithm. It's not unusual to be able to crack WEP in less than 5 minutes. This is because WEP used a very small (24-bit) initialization vector (IV) that could be captured in the datastream, and this IV could then be used to discover the password using statistical techniques.

Despite this, I still find it being used in household and small business implementations, but seldom in an enterprise environment.

WPA

WPA was the response by the industry to the revealed weaknesses of WEP. It's often referred to as WPA1 to distinguish it from WPA2.

WPA used Temporal Key Integrity Protocol (TKIP) to improve the security of WEP without requiring new hardware. It still uses WEP for encryption, but it makes the statistical attacks used to crack WEP much more difficult and time-consuming.

WPA2-PSK

WPA2-PSK is the implementation of WPA2 for the home or small business user. As the name implies, it's the WPA2 implementation that uses a pre-shared key (PSK). It's this security standard that is used by most households today, and although it's far more secure, it's still vulnerable to various attacks.

A feature that was added in 2007 called Wi-Fi Protected Setup, or WPS, allows us to bypass the security in WP2-PSK . We'll look at a few attacks on WPA2-PSK in coming weeks.

WPA2-AES

WPA2-AES is the enterprise implementation of WPA2. It uses the Advanced Encryption Standard or AES to encrypt data and is the most secure. It's often coupled with a RADIUS server that is dedicated for authentication.

Although cracking it is possible, it significantly more difficult.

Step 3: Channels

Like our radio, wireless has multiple channels so that various communication streams don't interfere with each other. The 802.11 standard allows for channels ranging from 1 thru 14.

In the U.S., the FCC regulates wireless communication and devices for use in the states are only enabled to use channels 1 thru 11. Europe uses channels 1 thru 13 and Japan 1 thru 14. Other nations may also use the full range.

For the hacker, this can be useful information as a rogue AP using channel 12 thru 14 would be invisible to U.S.-made wireless devices and security professionals scanning for rogue access points.

Each channel has a width of 22 Mhz around its central frequency. To avoid interference, an AP can use any of these channels, but to avoid any overlap, channels 1, 6, and 11 are most often utilized in the U.S. The other channels can be used, but because you need five channels between the working channels to not overlap signals, with three or more channels, only 1, 6, and 11 will work.

Step 4: Datagrams and Frames

An understanding of the structure of wireless datagrams is critical for successful wireless hacking, but is beyond the scope of this introduction. I will introduce some of this information when necessary in future tutorials, but you may want to take some time to study wireless frames and datagrams from other sources.

Step 5: Signal Strength

In the U.S., the FCC regulates among other things, the strength of the wireless access point's signal. The FCC says that the access point's signal cannot exceed 27 dBm (500 milliwatts). Most access points have this limit built-in, but we can change and override this limitation, if the access point is capable of a stronger signal. This may be useful for the hacker in setting up evil twins and rogue access points where strength of signal is critical, among other techniques.

Step 6: Aircrack-Ng

For nearly all of our Wi-Fi hacking, we will be using aircrack-ng which is included in BackTrack. Even in those hacks where we use other tools such cowpatty or reaver, we will use the aircrack-ng suite of tools for some part of the hack, so we need to become familiar with it.

I'll probably do a dedicated tutorial on aircrack-ng suite in the very near future.

Step 7: WiFi Adapters

One of the crucial needs to becoming an effective Wi-Fi hacker is the Wi-Fi adapter. Generally, the Wi-Fi adapter on your laptop or desktop is insufficient for our purposes. The key capability we need is the ability to inject packets into the access point and most run-of-the-mill wireless adapters are incapable of packet injection. Aircrack-ng has a list of Wi-Fi adapters that can work with their suite of tools.

That having been said, I highly recommend Alfa AWUS036NH USB wireless adapter. This is what I use. It's available from several locations for between $30 to $50.

It does everything I need, is fast, has an external antenna, is recognized by BackTrack, and automatically loads its drivers. In addition, it come in 1000mw and 2000mw versions. That can be critical in rogue access point hacks, despite the fact that the FCC limits signal strength the 500mw.

Step 8: Attennas

Antennas come in two basic types, omni-directional and directional. Most APs and wireless adapters come with omni-directional antennas, meaning that they send and receive in all directions.

The Alfa card that I recommend comes with an external antenna that is omni-directional, but has a gain of 5dBi (gain is a measure when applied to antennas, of how much the antenna can increase the signal). This means that it can increase the signal by focusing the signal similar to that of a reflector on a flashlight. In addition, it can change position to better receive particular signals as well as a cable and suction cup adapter for mounting on a wall or window.

Directional antennas can also be useful for hacking when attempting to focus your exploits to a remote access point. The literature contains references to Wi-Fi signals that have been sent and received over 100 miles or about 160km using directional antennas. For most commercial directional antennas, you can expect to be able to pick up wireless communication up to 4km or 2.4 miles.

These can be obtained from a variety of sources usually for under $100 with a gain of between 15dBi and 20dBi. A Yagi antenna is an example of a directional antenna that is often used in hacking wireless over significant distances.