Ubuntu/Kubuntu Tutorial.
Some times we require to change MAC address (Physical Address of network card).This can be temporarily or permanently. Here is a tutorial which illustrates changing  of MAC address in linux/ubuntu/kubuntu
To change the MAC address temporarily
Open terminal and type
ifconfig eth0 down

This command brings the network down 
Later type the following command.
ifconfig eth0 hw ether Your Mac Address

For example, it will be like
ifconfig eth0 hw ether 001B2F1359C3
Later bring the network up by the following command.
ifconfig eth0 up

Now type
dhclient

This DHCP protocol allows your computer to contact a central server …