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Communications over wireless links have been possible for a very long time. Radios were used for communications in the late 1800s. Guglielmo Marconi demonstrated the transmission of Morse Code over wireless links for the British Post Office in 1897. In 1898, the Russian navy cruiser Africa used a wireless communications device to communicate with operators on shore. Television signals were first broadcast in 1928. The very first visual image sent over television signals was Felix the Cat. Since those times, radio communications have come a long way. Commercial radio stations, television broadcasts, cellular phone networks, satellite data-links, slow-scan amateur video transmissions, baby monitors, Unmanned Aerial Vehicles (UAV), and GPS navigation systems all use wireless technology.
The use of encryption in communications is nothing new either. In fact, it's been used for centuries to protect sensitive messages, such as those sent from Caesar to his battlefield generals. The famous Enigma cipher machine was used during World War II to encrypt radio communications. Communications for television transmissions were encrypted with VideoCipher II in 1986. VideoCipher systems often used DES for video encryption. In 2001, the National Institute of Standards and Technology (NIST) in the United States selected Rijndael as a federal replacement for DES, thus naming Rijndael the new Advanced Encryption Standard (AES). AES has been incorporated in publicly available wireless communications devices as one of the algorithms for WPA. Some attacks are now available for AES, such as timing attacks that exploit the properties of certain types of hardware. Data encryption and communications security continue to remain an active area of research to this day.
The added convenience and capabilities offered by wireless technologies are not without a price, however. By offering new features and allowing for distributed operation, threats against the systems connected to wireless networks have increased. Break-ins to wireless networks are on the rise. The accessibility of wireless communications equipment has led to the proliferation of wireless networks and individuals who attack them. As wireless equipment becomes more ubiquitous, the economy of scale allows more individuals to acquire the hardware necessary to mount an attack against that equipment. The increasing amount of information and services available through wireless networks makes the systems connected to them much more attractive targets.
In order to understand the new threats a wireless network can pose, a basic understanding of radio frequency transmission and the technologies currently used to handle wireless communications is necessary.
Wireless equipment uses radio frequencies to communicate. These are electromagnetic emissions in the range of 3 Hz to 300 GHz. Although it creates electromagnetic emissions, a microwave oven is generally not considered a wireless device, as the radio waves are not used to communicate (sans firing a microwave oven at someone with a trebuchet). However, radio frequencies generated by other equipment are used for communications, such as those from cellular phones and Wi-Fi cards. These radio frequencies are received by the devices you want to communicate with to transmit information. They can also be received by devices you don't want to communicate with, exposing sensitive information.
Radio frequency transmissions are regulated by various organizations based on geographic boundary. At the international level, the International Telecommunications Union (ITU) coordinates the allocations of radio frequencies, and within the U.S., the Federal Communications Commission (FCC) regulates and enforces radio frequency allocations. The regulation of radio transmissions by the various regional bodies ultimately affects the design and deployment of wireless networks. Radio frequency propagation issues that are present in one regional area may not be an issue in another due to regional allocations. For example, the frequencies from 222 MHz through 225 MHz are available for some amateur radio use in the U.S., but in the U.K., those frequencies are marked for military use. As such, wireless device manufacturers have to be cognizant of regional differences so users of the devices are within regulatory compliance for their region.
The wireless technology standards recognize these regional differences and specify frequency allocations and transmission standards that allow interoperability within the various regulatory domains. The Institute of Electric and Electronics Engineers (IEEE) has taken these regional differences into account when designing and ratifying wireless networking standards. One visible aspect of these regulatory controls is the numbering of transmission channels in the IEEE 802.11X standards (the "X" in 802.11X is a placeholder for other letters; there is no 802.11X standard per se). Different regulatory domains have access to different channels, and the numbering of channels may be discontinuous when viewed by the user. When examining the list of available wireless channels on 802.11 devices, you might have noticed certain channel numbers are "missing"; the missing channels are transmission bands removed or disabled due to regional emissions regulations.
The wireless hardware commonly found in laptops and home networking equipment is usually based on 802.11X protocols. Computers without a wireless transmitter can generally use an add-on product to connect to 802.11X networks. Many vendors offer wireless cards for laptops, expansion cards for workstations, and built-in print servers with a wireless transmitter that connects directly to a printer.
Bluetooth is another common wireless communications protocol. The Bluetooth protocol is often used for devices such as cellular phones, headsets, digital cameras, and other devices not often viewed as being "computers." Wireless headsets for cellular phones are often Bluetooth devices. Cellular phones that offer calendar and address book synchronization capabilities with software running on a user's laptop often employ the Bluetooth protocol. You can use a keyboard and mouse over the protocol as well, employing Bluetooth to connect them to the computer.
Unlike the IEEE 802.11X protocols, the Bluetooth protocol was designed to connect small, portable devices into a personal area network (PAN). Often, the devices have minimal processing capability, low power consumption, and usually communicate with a device less than a couple meters away. The Bluetooth protocol was developed by the Bluetooth Special Interest Group (SIG). While the protocol was not created by the IEEE, the 802.15 Work Group (WG) for Wireless Personal Area Networks (WPAN) has announced its adoption of Bluetooth as the foundation of their 802.15 standards work. The rights to the standard have been transferred to the IEEE for further development.
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