changing MAC address questions

I have couple questions regarding MAC address changes:

1) When we change the MAC address, it will change the firmware of NIC,
or just temporary change?
My observation is just temporary change.

2) Do you think changing MAC address can secure the machine more? I
mean at least hackers
cannot keep track on the machines that easily? Well, maybe hackers
should use IP address,
but my observation is that when I change the MAC address, IP address
will change as well.

3) I try it myself, when I change the MAC address, it will change the
IP address as well.
IP address is assigned by ISP, maybe ISP assigns the IP address based
on the MAC address
of the machine as well? MAC address identifies the network card, and IP
address identifies
the computer on the internet.

Please advise. thanks!!

[POSTED TO alt.internet.wireless - REPLY ON USENET PLEASE]

In <(E-Mail Removed) .com> on 10 Oct 2005
07:42:25 -0700, (E-Mail Removed) wrote:

>2) Do you think changing MAC address can secure the machine more? ...

No.

--
Best regards, HELP FOR CINGULAR GSM & SONY ERICSSON PHONES:
John Navas <http://navasgrp.home.att.net/#Cingular>

On 10 Oct 2005 07:42:25 -0700, *email_address_deleted* wrote:

>I have couple questions regarding MAC address changes:
>
>1) When we change the MAC address, it will change the firmware of NIC,
>or just temporary change?
>My observation is just temporary change.
>
>2) Do you think changing MAC address can secure the machine more? I
>mean at least hackers
>cannot keep track on the machines that easily? Well, maybe hackers
>should use IP address,
>but my observation is that when I change the MAC address, IP address
>will change as well.
>
>3) I try it myself, when I change the MAC address, it will change the
>IP address as well.
>IP address is assigned by ISP, maybe ISP assigns the IP address based
>on the MAC address
>of the machine as well? MAC address identifies the network card, and IP
>address identifies
>the computer on the internet.
>
>Please advise. thanks!!

IMHE, changing your MAC address is a useless method of providing security, and
can cause worse problems.
# It is a form of Security by Obscurity.
<http://nitecruzr.blogspot.com/2005/05/security-by-obscurity.html>
# The MAC address is the lowest level identity in networking. See OSI model to
understand this
(<http://nitecruzr.blogspot.com/2005/05/security-by-obscurity.html> for
example). You absolutely must have a unique MAC address on all networked
devices. If you go changing this identity element, and cause a conflict, you
could cause yourself and other people grief.
# If you change your MAC address in an attempt to change your IP address on a
public Internet service, you could cause pain for a few people, including
another subscriber, and the ISP. Changing your IP address is another form of
Security by Obscurity.

--
Cheers,
Chuck, MS-MVP [Windows - Networking]
http://nitecruzr.blogspot.com/
Paranoia is not a problem, when it's a normal response from experience.
My email is AT DOT
actual address pchuck mvps org.

(E-Mail Removed) wrote:

> I have couple questions regarding MAC address changes:
>
> 1) When we change the MAC address, it will change the firmware of NIC,
> or just temporary change?
> My observation is just temporary change.

As far as I know, it's temporary.

>
> 2) Do you think changing MAC address can secure the machine more? I
> mean at least hackers
> cannot keep track on the machines that easily? Well, maybe hackers
> should use IP address,
> but my observation is that when I change the MAC address, IP address
> will change as well.

It makes no difference for security. MAC addresses are relevant only on the
local network. They are discarded as soon as your packets pass through a
router.

>
> 3) I try it myself, when I change the MAC address, it will change the
> IP address as well.
> IP address is assigned by ISP, maybe ISP assigns the IP address based
> on the MAC address
> of the machine as well? MAC address identifies the network card, and IP
> address identifies
> the computer on the internet.

The ISP doesn't assign an IP address based on the MAC address. It assigns a
new address to what appears to be a new computer. It won't reassign the
previous one, until the lease expires.

Chuck wrote:

> You absolutely must have a unique MAC address on all networked
> devices. If you go changing this identity element, and cause a conflict,
> you could cause yourself and other people grief.

The MAC only has to be unique on the local network. It's irrelevant
elsewhere.

Answer to

1) The MAC address will/should be changed permanently in the firmware. You
need to do this only in special cases, especially when your Internet service
provider instructs you do this!

2) NO! The MAC is not a security service. Whenever the MAC changes, the
network card is told to be a different unit and another IP address is
issued. Use a firewall.

3) See complete description of answer 2. MAC address identifies the PC to
the network. ISP DHCP service locates new MAC address on their systems. IP
address does not identify your PC to the Internet. IP address provides the
"signals" so that your PC can "talk" with the Internet. The IP addresses
identifies your ISP only.


<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
>I have couple questions regarding MAC address changes:
>
> 1) When we change the MAC address, it will change the firmware of NIC,
> or just temporary change?
> My observation is just temporary change.
>
> 2) Do you think changing MAC address can secure the machine more? I
> mean at least hackers
> cannot keep track on the machines that easily? Well, maybe hackers
> should use IP address,
> but my observation is that when I change the MAC address, IP address
> will change as well.
>
> 3) I try it myself, when I change the MAC address, it will change the
> IP address as well.
> IP address is assigned by ISP, maybe ISP assigns the IP address based
> on the MAC address
> of the machine as well? MAC address identifies the network card, and IP
> address identifies
> the computer on the internet.
>
> Please advise. thanks!!
>

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
>I have couple questions regarding MAC address changes:
>
> 1) When we change the MAC address, it will change the firmware of NIC,
> or just temporary change?
> My observation is just temporary change.
Temporary.
>
> 2) Do you think changing MAC address can secure the machine more? I
> mean at least hackers
> cannot keep track on the machines that easily? Well, maybe hackers
> should use IP address,
> but my observation is that when I change the MAC address, IP address
> will change as well.
No, I don't see how just changing the MAC address makes much difference.
Since the ISP only controls a range of IP addresses, all a hacker needs to
do is ping everyone of them, and try to penetrate those that respond. This
method would work whether you changed the MAC address or not.
>
> 3) I try it myself, when I change the MAC address, it will change the
> IP address as well.
> IP address is assigned by ISP, maybe ISP assigns the IP address based
> on the MAC address
> of the machine as well? MAC address identifies the network card, and IP
> address identifies
> the computer on the internet.
Perhaps they do. However, this is merely security by obscurity.
Jim
>
> Please advise. thanks!!
>

On Mon, 10 Oct 2005 14:02:44 -0400, James Knott <*email_address_deleted*> wrote:

>(E-Mail Removed) wrote:

>> 3) I try it myself, when I change the MAC address, it will change the
>> IP address as well.
>> IP address is assigned by ISP, maybe ISP assigns the IP address based
>> on the MAC address
>> of the machine as well? MAC address identifies the network card, and IP
>> address identifies
>> the computer on the internet.
>
>The ISP doesn't assign an IP address based on the MAC address. It assigns a
>new address to what appears to be a new computer. It won't reassign the
>previous one, until the lease expires.

And if you try to connect using a MAC address currently in use by another
customer, what happens? If you appear to be an already known customer
(previously seen MAC address), will it assign the same IP address, will it
declare that IP address in use and assign another address, or wilt it declare an
unidentified problem and maybe disconnect both instances of the same MAC
address?

--
Cheers,
Chuck, MS-MVP [Windows - Networking]
http://nitecruzr.blogspot.com/
Paranoia is not a problem, when it's a normal response from experience.
My email is AT DOT
actual address pchuck mvps org.

Since MAC addresses don't travel off the local area network, unless you
got some VLAN stuff going on, the chances are just a tiny bit small

Chuck wrote:
> On Mon, 10 Oct 2005 14:02:44 -0400, James Knott <*email_address_deleted*> wrote:
>
>
>>(E-Mail Removed) wrote:
>
>
>>>3) I try it myself, when I change the MAC address, it will change the
>>>IP address as well.
>>>IP address is assigned by ISP, maybe ISP assigns the IP address based
>>>on the MAC address
>>>of the machine as well? MAC address identifies the network card, and IP
>>>address identifies
>>>the computer on the internet.
>>
>>The ISP doesn't assign an IP address based on the MAC address. It assigns a
>>new address to what appears to be a new computer. It won't reassign the
>>previous one, until the lease expires.
>
>
> And if you try to connect using a MAC address currently in use by another
> customer, what happens? If you appear to be an already known customer
> (previously seen MAC address), will it assign the same IP address, will it
> declare that IP address in use and assign another address, or wilt it declare an
> unidentified problem and maybe disconnect both instances of the same MAC
> address?
>

Chuck wrote:

> And if you try to connect using a MAC address currently in use by another
> customer, what happens? If you appear to be an already known customer
> (previously seen MAC address), will it assign the same IP address, will it
> declare that IP address in use and assign another address, or wilt it
> declare an unidentified problem and maybe disconnect both instances of the
> same MAC address?

I suspect that would depend on the ISP.