RC4 uses a pseudo random number generator (PRNG)
to create the keystream. PRNG does not create a true
First 256 bytes of the RC4 cipher can be determined
RC4 source code (or a derivation) has been revealed
Attackers can see how the keystream itself is
WEP attack tools
AirSnort, Aircrack, ChopChop WEP Cracker, and WEP
Crack (all freely available on the internet).