Apparatus for eavesdropping within an area layer adjacent to and
surrounding a LAN area periphery for potential wireless transmissions of
an intruder having a lower frequency within a level below the LAN
frequency; and an implementation responsive to said eavesdropping
apparatus for changing the encryption code of said encrypted wireless
transmission upon the eavesdropping detection of a wireless transmission
of said lower frequency addressed to a network location of one of the
terminals in said LAN.