Windows lets the user enter the details for hidden networks, and then, enticingly, offers to watch for the network and connect automatically when in range. Imagine a wireless network named “Thunder Dome." Normally, the server sends out a message at a fixed interval saying, “I am Thunder Dome." Other devices can see the network and recognize it by name. Now let’s turn off the SSID. The router no longer brags about itself, but what does the laptop do? If the user has it set for automatic connections, it says, “Yoo-hoo, Thunder Dome, are you here? Yoo-hoo, Thunder Dome, where are you?"
So if the laptop is going to blab, what’s the use of hiding the network?
WEP was originally designed to use a 40-bit security key. 40 bits is five bytes, and there are 240 (a really large number) possible key combinations. Even though that is a large number, small computers can defeat a 40-bit key by using a “brute force" attack that consists of running through all of the possible combinations until a match is made.