Friday, December 10, 2010

missile command and mac addresses

Network access blocking using MAC addresses is sometimes like missile command or whack-a-mole depending... you find an errant client, and you tell your firewall-router to block said MAC. What do you do if you're on the receiving end? Change the MAC programmatically, of course.

My ethernet controller is eth0 and has MAC address (or Hardware Address) is 00:0f:1f:f7:b1:64 . I know that there are no MACs with HWaddr 00:0f:1f:f7:b1:65 on the network. Let's change that MAC address.
# ifconfig eth0 down
# ifconfig eth0 hw ether 00:0f:1f:f7:b1:65
# ifconfig eth0 up
Take that! Now, you can very very easily have a little tee script and substitute away every time you're disallowed. But, come on, what tomfoolery are you up to that'd make you programatically denied network access?
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