Network Interface Cards

Wireless network interface cards (NICs) now offer the stronger 128-bit
encryption schemes and have their own unique media access control
(MAC) addresses that identify that card on your network. They also possess their own public and private key pairs to maintain a straightforward
method of encryption to the WLAN. These unique identifiers allow
you to use these MAC addresses as a means of access control to allow
only specified NICs onto your network. You can program your access
points (wireless routers) to look for this unique hardware NIC identifier
and permit only that address to access your network resources. This
entire exchange is completely transparent to the user, doesn’t consume
any extra network bandwidth, and maintains a higher level of security.
Should someone attempt to log onto your network with an unauthorized
network card from the parking lot in front of your business offices, the
access point would automatically determine that the MAC address of
the hacker’s wireless NIC card is not on the authorized user list and
deny access.
You can also program some wireless routers/access points to maintain
a log of all the MAC address combinations they see and then reject any
addresses they don’t recognize. This method allows you to prevent a
hacker from attempting to break into your network by trying to spoof
the MAC address of his NIC card to emulate an address of a card that is
authorized to access your network.