802.11 Security

Chapter 1. A Wireless World

Wireless networking is revolutionizing the way people work and play. By removing physical constraints commonly associated with high-speed networking, individuals are able to use networks in ways never possible in the past. Students can be connected to the Internet from anywhere on campus. Family members can check email from anywhere in a house. Neighbors can pool resources and share one high-speed Internet connection.

Over the past several years, the price of wireless networking equipment has dropped significantly. Wireless NICs are nearing the price of their wired counterparts. At the same time, performance has increased dramatically. In 1998, Wireless Local Area Networks (WLAN) topped out at 2Mb/s. In 2002, WLANs have reached speeds of 54Mb/s and higher.

Unfortunately, wireless networking is a double-edged sword. Wireless users have many more opportunities in front of them, but those opportunities open up the user to greater risk. The risk model of network security has been firmly entrenched in the concept that the physical layer is at least somewhat secure. With wireless networking, there is no physical security. The radio waves that make wireless networking possible are also what make wireless networking so dangerous. An attacker can be anywhere nearby listening to all the traffic from your network—in your yard, in the parking lot across the street, or on the hill outside of town. By properly engineering and using your wireless network, you can keep attackers at bay.

This chapter serves as an introduction to wireless networking and some of the high-level security concerns. Building a secure wireless network requires a wide breadth of knowledge; from the low-level aspects of radio transmission to understanding how various applications interact with the network. By understanding how all aspects of the network interact, you can safely and freely use wireless networks.

What Is Wireless?

The term wireless means different things to different people. In general, the term reflects any means of communication that occurs without wires. In this buzzword-compliant time, many of the following terms are synonymous with the word wireless:

• PCS

• WAP

• WTLS

• WML

• 802.11b

• Wi-Fi

• HomeRF

• Bluetooth

While all these terms mean “wireless” to some, most refer to different technologies. Personal Communication Systems (PCS) is a standard for cellular communication. Wireless Application Protocol (WAP) is mechanism of distributing data to lightweight wireless devices. Wireless Transport Layer Security (WTLS) performs for WAP the same role SSL does for web traffic. Wireless Markup Language (WML) is a lightweight markup language similar to HTML but designed to be rendered on small screens with low bandwidth use.

HomeRF and the 802.11 standards are competing wireless LAN protocols. They are analogous to protocols such as 802.3 Ethernet on wired networks. 802.11 is a standard developed and ratified by the Institute of Electrical and Electronics Engineers (IEEE). 802.11 products approved by the Wireless Ethernet Compatibility Alliance, are branded with the Wi-Fi mark to certify interoperability. HomeRF on the other hand is a standard developed by a group of corporations and lacks international recognition. Intel, one of the primary backers of HomeRF, stopped producing HomeRF equipment in late 2001 in favor of 802.11. In general, the majority of WLANs in use today are based on the 802.11 standard.

Bluetooth is another popular wireless network standard. Bluetooth networks operate on a smaller scale than a LAN. A network of Bluetooth devices is typically referred to as a Personal Area Network (PAN). Bluetooth enables personal devices such as cell phones, personal digital assistants, and watches to communicate. Bluetooth was designed to operate in small areas (about the size of a cubicle) with very low power consumption.

There are many reasons people choose to deploy a WLAN:

• Increased productivity due to increased mobility

• Lower infrastructure cost compared to wired networks

• Rapid deployment schedules

• Aesthetically unobtrusive

Wireless LANs are being deployed at a rapid rate but with little regard to security. This book focuses on wireless LANs in general and 802.11-based networks in particular and will attempt to outline strategies and implementations that you can use to deploy a secure wireless network.