MAC Address

[Alex Satrapa]

On Friday, October 18, 2002, at 03:26 , ht lee wrote:

> I was reading about the insecurity of 802.11b and I was just curious 
> why would the vendors allow the MAC address of a wireless network to be 
> changed?

Because it's easy to do so.

Some companies want to change the MAC addresses of their equipment to 
make it harder to guess what kind of hardware they're using.  From the 
factory, ethernet addresses are part of a particular block of addresses 
that are assigned to that company.  For example, given the MAC address 
"00:80:c8:*:*:*" I can guess that the machine is using a DEC ethernet 
card.

If a malicious person knew that particular network cards had known 
problems (unable to handle large packets, timing issues, etc), they 
could use those problems to DoS the target machine.

So if you modify the MAC addresses of all your machines to some range 
that is privately known to your company, you can avoid these issues.  
Having "corporate standard" MAC ranges also makes it easier to detect 
which network devices are not company issue.

There are many other legitimate reasons why you'd want to change the MAC 
address.

By making MAC address mangling easy, the suppliers are also reminding 
people not to rely on MAC addresses for security (whether they intended 
to do so or not is a different question).

Alex

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