I did a short series on attacking Wi-Fi for my personal blog last year, but I did not cover Enterprise Wireless. A few interesting tools have been released in the time that has passed, so I’m going to steal some of my own words as a short lead into a new post on conducting attacks against WPA/2-Enterprise wireless networks.
Electromagnetic energy is the basis on which all modern day wireless communication systems are based. Radio, non-cable television, cellular and satellite phones, and WiFi all rely on signals carried over the air within the various bands of the radio frequency (RF) spectrum. Below is a breakdown of these bands:
Math and General Terminology
WiFi operates by design within the Ultra High Frequency (UHF) and Super High Frequency (SHF) bands at 2.4 and 5 GHz respectively. Before we start exploring WiFi as a service, it’s important to sort out the relevant terminology and functionality of RF theory as a whole.
Amplitude is the height of a wave. It is measured from a wave’s midpoint to its peak. It is normally expressed in Volts (V).
Frequency refers to the number of times a wave cycles past a given point each second. It is normally expressed in Hertz (Hz).
Wave Length is the distance from the start to the end of a single wave cycle. It is typically expressed in meters.
Relative power (dB) = 10 Log^10 [P1 (watts) / P2 (watt)]
Fortunately, there is an easy pair of rules to help remember the relationship: The Rules of 3 and 10. Duplicating the power is equal to adding 3 dB, and reducing the power by half is equal to subtracting 3 dB. Multiplying the power by ten is the equivalent of adding 10 dB, and reducing the power by one tenth is equal to subtracting 10 dB. On the right is a chart that will better illustrate this relationship.
A wave is simply a transfer of energy by oscillation from one location to another. Electromagnetic waves travel at a constant rate (the Speed of Light: 299 792 458 m/s…or ~300 million m/s). RF waves travel outward from a source not unlike the ripples in a pond where a rock has been dropped, though the propagation patterns of RF energy are greatly affected by a number of environmental factors.
When a wave changes mediums, a portion of the wave will continue to propagate through the new medium. This is known as Refraction. The angle at which the wave continues to travel depends on the make-up of the two mediums.