Re: Microsoft and MACs

[Nicholas Petreley <nicholas@petreley.com>]

Here's another wrinkle I discovered by accident - if you install 
Windows 98 with one NIC and then change the NIC, the ID number is 
not updated.  It continues to use the original MAC address (from 
the old card).  

-Nick

"Eric M. Bennett" wrote:
> 
> Paul Rickard wrote:
> 
> >From:                  Nicholas Petreley <nicholas@petreley.com>
> >
> >> Has anyone explored why Microsoft would want to tie user data
> >> to network MAC addresses?  Why would anyone want a MAC address
> >> except to sniff or spoof network packets?
> >
> >       Because like fingerprints and social security numbers, the MAC
> >address on every modern network card is unique. Unless someone switches
> >NICs around or changes their computer, you can tell who they are by the
> >MAC.
> 
> This is not correct.
> 
> Some NICs are reconfigurable.  For example, Apple Computer used to
> distributed an unsupported program called "Apple LAN Utility" which could
> be used to change the MAC address sent out by the machine on its ethernet
> packets.
> 
> I used this feature when I was an undergraduate at Penn State.  The dorm
> networks and routers there were reasonably secure... each ethernet jack
> would only accept packets marked with a specific MAC address, and only
> received packets destined for the MAC address associated with that jack.
> The goal was to prevent packet sniffing.  But when there was a network
> problem, you couldn't just plug in another computer to see if the port was
> working, because the port was programmed to reject other MAC addresses.  So
> I found Apple LAN Utility useful as a diagnostic because I could
> reconfigure my Mac to look just like the machine that was having trouble
> with the port, and I could test the port with my own computer.  Doing this
> isolated the problem: a bad computer setup or card vs. a problem with the
> wall jack.
> 
> I believe some other network card vendors have included this feature.  MAC
> addresses cannot be considered to be secure.
> 
> --
> Eric Bennett ( http://www.pobox.com/~ericb/ )
> Department of Chemistry & Chemical Biology, Cornell University
> 377 Olin Chemistry Lab
> 
> A designer knows he has achieved perfection not when there is
> nothing left to add, but when there is nothing left to take away.
> -  Antoine de Saint-Exup'ery

-- 

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Nicholas Petreley 
IDG Conferences, LinuxWorld,
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nicholas@petreley.com
http://www.petreley.com
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