WEP isn't really all the secure. There is a tool called aircrack and airsnort that can crack a wep key in as little as 3 minutes. Anyone heard of this before?
First of all WEP, short for Wired Equivalent Privacy, is used at the two lowest layers of the OSI model - the data link and physical layers; it therefore does not offer end-to-end security.
WEP has three settings: Off (no security), 64-bit (weak security), 128-bit (a bit better security). WEP is not difficult to crack, and using it reduces performance slightly.
If you want the best wireless encryption, use WPA if available.