Security Basics mailing list archives

RE: Strange pings from 127.0.0.1


From: Steven Trewick <STrewick () joplings co uk>
Date: Thu, 24 Jun 2004 10:15:33 +0100


Next, (assuming non-promiscuous mode of operation by the NIC) I fail to
understand how the author of this attack intends to reach his/her targets,
if the dest MAC addresses are fake! I might be missing something obvious,
so if someone can point it out to me, that would be great. thanks.

The OP doesn't say what the SRC and DEST MAC are, (which would be helpful),
but its entirely possible that they are multicast MAC addresses, which
would be broadcast to every switch port.

This is not always obvious if you don't know what to look for,
multicast MAC addresses are identifiable by the low order bit of 
their first byte, if this is set to 1, (eg the byte is odd) the frame 
is multicast.

To take an example, if the destination MAC address is 01:xx:xx:xx:xx:xx 
then it is a multicast address, same for 03:xx:xx:xx:xx:xx, but not
for 02::xx:xx:xx:xx:xx

See http://www.iana.org/assignments/ethernet-numbers for a discussion
of MAC addressing in general, and an explanation (?) of MAC multicast

While I doubt this is related to the OP's problem, I hope it will
prove useful.






















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