Security Basics mailing list archives

RE: A Solution for sniffing


From: "Chris Berry" <compjma () hotmail com>
Date: Thu, 19 Dec 2002 15:36:08 -0800

From: <David () cawdgw net>
For a network card to "Sniff" it must be in promiscuous mode, reading
all packets coming in and not dumping those not addressed to it.
Google the web for tools that can find network interface cards in
promiscuous mode. I can think of only two legit reasons to be in that
mode: some firewall/IDS's need
that mode to pull in all packets, and someone sniffing the network with
permission. Therefore, after you look and find a netcard in promiscuous
mode, you can check the system files for WHY it is in that mode.

As far as hardware sniffers, Someone else will have to say it with
authority. I think the technique that finds software driven promiscuous
netcards works on hardware sniffers, but I may be wrong.

Ok, I'm a bit confused. As I understand ethernet, all the signals go out on the wire as changing voltage levels, every card listens to the signals and internally decides whether or not to drop the frames based on whether or not they are destined for its MAC address. With a passive listening setup like this, how could you possibly detect a promiscuous interface?

Chris Berry
compjma () hotmail com
Systems Administrator
JM Associates

"Live dangerously, overclock your servers."

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