Vulnerability Development mailing list archives
Re: spoofing the ethernet address
From: harnold () BINGHAMTON EDU (Arnold, Jamie)
Date: Tue, 14 Mar 2000 11:15:37 -0500
I have a question that one/some of you may be able to help with. We have a user in one of our dorms (DHCP) that is reporting his MAC address as changing about every 10 minutes. When he first powers-on his system, the MAC is correct and DHCP renews his lease. After a while, the master switch shows his IP having about 10 different MAC addresses, all variations of the first where the first 4 digits remain constant, the second 4 go to the last position and the middle 4 change randomly. Has anyone seen this, or have any idea what's going on. My theory is a cheap NIC with bad firmware. We have seen an influx of inexpensive cards coming into campus that have had duplicate MACs or no MACs (000000000000) at all. Thanks ****************************************************** Jamie Arnold Binghamton University Lead Programmer/Analyst PO Box 6000 607-777-4229 voice Vestal Parkway East 607-777-6147 fax Binghamton, NY 13902 harnold () binghamton edu www.binghamton.edu ****************************************************** <'}}}>< "Life was simple before World War II. After that, we had systems." Admiral Grace Hopper -----Original Message----- From: Timothy J. Miller [mailto:timothy.miller () AFIWC01 AF MIL] Sent: Monday, March 13, 2000 8:37 AM To: VULN-DEV () SECURITYFOCUS COM Subject: Re: spoofing the ethernet address "Buhrmaster, Gary" <gtb () SLAC STANFORD EDU> writes:
It is my hazy recollection that while some TR cards didn't have a promiscuous mode, the important item was that the specification required that if you enabled promiscuous mode, the card was supposed to announce that fact on the ring so that everyone now knew that someone was listening (and the "management station" could go out and smack someone).
Correct.
Of course there were ways to get around that announcement, there always are, but it showed some thought about the issues.
In my experience, TR cards are fairly notorious for not doing what they're supposed to. For example, we had a condition on one of our rings where MAC address test packets were being incorrectly responded to, but only certain revisions of the TR cards on the ring were properly kicking themselves out. *That* one took some time to figure out, (using a TR sniffer, as it happened) let me tell you. 8/
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