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OK - I have a static IP - and I have been on the same provider for years - its a wired network (a cable goes directly to my network card) - and the cable is connected to a switch on a pole in the street (the pole is connected to another pole which also has a switch for several houses etc) - basically whole city is connected in this manner

Using wireshark about 4-5 months ago while filtering packets for dhcp - I could discover other users "mac addresses" (that were on the same network on the same ISP) - and simply by changing my mac address to one of theirs - I would be transfered on their bandwidth, and I would be assigned a new IP by the ISP for that mac address.

Now, after they reworked their network, even if I change the mac address I can't gain access to internet, like before.


Why was I able to get connected to other user's mac addresses and surf the internet using their bandwidth?

And why I can't do that now? What has the ISP done to prevent it?

NOTE: I am not looking here to learn how to steal the internet but I simply wonder what catastrophic vulnerability the ISP hasn't noticed until very recently.

Thanks in advance for your answers.

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closed as off topic by EEAA, Chris S Apr 24 '12 at 2:42

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My guess is they've locked it down so that they filter the traffic that comes from a mac address that shouldnt be on that switch port. This is a very common network security practice. – Patrick Apr 24 '12 at 2:36

They used to not lock the MAC address to the port, now they do.

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