How Do Wireless Networks Work?
As the name suggests, wireless networks, sometimes called WiFi, allow a user to connect to the Internet without relying on wires. If your home, office, airport, or even local coffee shop has a wireless connection, you and your employees can access the network from anywhere that is within that wireless area.

Wireless networks rely on radio waves rather than wires to connect computers to the Internet. A transmitter, known as a wireless access point or gateway, is wired into an Internet connection. This provides a "hotspot" that transmits the connectivity over radio waves. Hotspots have identifying information, including an item called an SSID (service set identifier), that allow computers to locate them. Computers that have a wireless card and have permission to access the wireless frequency can take advantage of the network connection. Some computers may automatically identify open wireless networks in a given area, while others may require that you locate and manually enter information such as the SSID.

Basic Preparedness Tips for Protecting Wireless Networks

• Change default passwords
• Treat wireless network as an “Internet”
• Maintain anti-virus and anti spyware software
• Install a firewall
• Use hardware address (MAC) access control
• Change the default identifiers
• Use WEP (Wired Equivalent Privacy) wisely
• Change default keys and change often
• Use a VPN over a wireless network

What Security Threats Are Associated With Wireless Networks?
Because wireless networks do not require a wire between a computer and the Internet connection, it is possible for attackers who are within range to hijack or intercept an unprotected connection.  Vulnerabilities associated with wired networks also apply to wired, making current protection software essential.

Resources: 
National Cyber Alert System Tip: Securing Wireless Networks