Subtle Attacks

Another problem possible on your 802.11 WLAN is a WEP attack where
a hacker initiates an active attack while simultaneously deciphering
data channel packets by altering their information and CRC and then
transmitting these altered bits of information back to the access point.
There is a great deal of risk associated with the creation of encryption
protocols that do not possess a cryptographic privacy protection mechanism
due to the communication necessary with several other protocol
levels that can leak information about your encrypted data.