Wi-Fi networks, based on the IEEE 802.11 b/g standards, have become very popular in recent years. Many users have installed Wi-Fi networks at home, and numerous corporations have added Wi-Fi access points to their wired networks, giving employees easier access to corporate data and services. Hackers can decrypt and read data on a wireless link protected by built-in WEP encryption, and may even be able to access the data on a wired network through a Wi-Fi access point. We assess Wi-Fi network security in one city, analyze alternative security techniques, and suggest ways to secure such networks.