When authentication or filtering is based on the hardware address, we can use hardware address spoofing. The hardware address appears in the ifconfig output as HWaddr 00:1c:bf:87:25:d2.

The hw subcommand of ifconfig will define a devices class and the MAC address:

# ifconfig eth0 hw ether 00:1c:bf:87:25:d5 

In the preceding command, 00:1c:bf:87:25:d5 is the new MAC address to be assigned. This is useful when we need to access the Internet through MAC-authenticated service providers that provide access to the Internet for a single machine.