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I am selling my old docsis cable modem, and my buyers' frequently asked question is "is it not stolen/blacklisted?"

Will I have problems if I post the modem's MAC addresses on my online ad? I mean will a hacker be able to get it banned or void my modem or spoil my sale with this information?

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Just post a fake one on the ad, or one a few digits off. If there's no problem with the modem itself, who cares? Don't overcomplicate things, a MAC address can be spoofed/changed for a reason. –  Breakthrough Jan 30 '12 at 12:22
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3 Answers

up vote 3 down vote accepted

If a person has your MAC address they spoof their MAC address and use yours, though the chance is small. The only possible consequence would be that the ISP blocks the MAC. If you would call to the ISP they can just unblock it if it is clear you did nothing. But I repeat, this scenario is very unlikely.

A modem cannot be universally blocked by its mac, only by a single provider that detects abuse.

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Do hackers need to go around hunting for a real modem's MAC address? Can't they just add a random NIC numbers to a given OUI number, if this is their intention? This isn't like a Windows product key, right? Plus, the hacker won't know what my eventual buyer's ISP will be. –  William C Jan 30 '12 at 11:31
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Hackers can just choose a random MAC, the chance they take yours is very small. The MAC is just the identifier for layer 2 of the OSI model, no windows key ;) –  Robert Jan 30 '12 at 11:46
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I wouldn't do it. Somebody could change a MAC to fit the one on your online ad.

As an alternative, you could send it privately to future buyers if they request it.

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"Future buyers" could change a MAC to fit the one I sent privately to them.. Doesn't all this do is give me more work? –  William C Jan 30 '12 at 11:01
    
@WilliamC: They are asking you, sending it privately keeps you from having the MAC address out in the open. It's the least you can try to do as a security measure. And well, you'll have the names of the people that have your MAC address... –  Tom Wijsman Jan 30 '12 at 11:27
    
If the "future buyer" changes his own MAC address to match yours, this will not allow him to steal service nor cause you a problem. The reason is because BPI+ would prevent him from ever signing on successfully. The old guides on the internet about MAC address cloning are pre-BPI+ information. As of quite some years ago, it is outdated and useless. –  snacky Jan 15 '13 at 1:40
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Post the RF MAC address. It won't cause you a problem. Unless it's a very antiquated DOCSIS 1.0 modem - but, in that case, these concerned buyers won't want it anyway.

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