Security has always been a concern with Wi-Fi because the network boundary has moved. Wireless signals can travel through solid matter, such as ceilings, floors, walls, outside of the home, or office space. Without stringent security measures in place, installing a WLAN can be the equivalent of putting Ethernet ports everywhere, even outside.

To address the threats of keeping wireless intruders out and protecting data, two early security features were used:

Although these two features would deter most users, the reality is that neither SSID cloaking nor MAC address filtering would deter a crafty intruder. SSIDs are easily discovered even if APs do not broadcast them and MAC addresses can be spoofed. The best way to secure a wireless network is to use authentication and encryption systems, as shown in Figure 1.

Two types of authentication were introduced with the original 802.11 standard:

The chart in Figure 2 summarizes the various types of authentication.