WEP Mechanics

WEP is designed to prevent someone from casually eavesdropping or
modifying any portion of your data stream. WEP uses an RC4 40-bit
stream cipher to encrypt data and a 32-bit CRC to verify it. Unfortunately,
it has a faulty algorithm, so that several types of attacks can succeed
against it. The biggest problem with the algorithm is that RC4 is subject
to key-steam reuse, which basically destroys the ability for it to encrypt
information effectively. Attacks against the RC4 algorithm involve collecting
frames for statistical (traffic) analysis, using SPAN to decrypt
frames, and “flipping” data so that messages and information are altered.