Wii can use WEP, WPA (TKIP or AES) and WPA2 (AES).
WEP is the least secure of these types of wireless security. The WPA (TKIP) is the second-most secure, as the security device itself assigns individual keys to its connecting devices and changes them regularly. WPA2 is considered the most secure with its level of protection, and is preferred in any devices capable of using it.
WPA encryption types function very similarly to WEP encryption.
If an Access Point appears as a lock, you will need to enter a WEP or WPA key on your Wii console to use the Access Point. Click on the appropriate type of security setting and you will be prompted to enter the key.