On Sat, Mar 23, 2002 at 10:12:48AM -0000, tcpdump-workers wrote:
> Is there a way to sniff networking usin a modem.
Only if the network you're sniffing on is using the modem.
I.e., if you are running SLIP or PPP over the modem, *and* the OS on
which you're running allows tcpdump (or other libpcap-based sniffers) to
capture on SLIP or PPP links, you can sniff the traffic on that modem.
> This is the scenario:
> Two compuers connected to the same phone line , noth using a modem
> (28,800) - to connect to the net.
> Obviously they can't be connected to the net together - but can one
> comuter sniff the other host?.
Not with tcpdump (or any other libpcap-based sniffer). If one computer
is dialed in and running a network connection over the model using SLIP
or PPP, *that* computer might be able to sniff its own connection (if
the OS allows it), but the other computer cannot use a libpcap-based
sniffer to do that.
> I thought tcpdump can do it , but when I typed ifconifg
> I can't see the modem , any ideas?
If you ran ifconfig on the machine that *wasn't* dialed in, the reason
why you can't see the modem is that it's not dialed in, and therefore
there *is* no SLIP or PPP interface for it.
There are a couple of things that *might* work:
possibility 1:
There might exist some form of hardware that could plug into the
phone line and watch the signals going down it, feeding them to
a modem or something else that could turn it into a bit stream,
that you could somehow connect to the other computer.
That computer would have to be running some kind of software to
capture that bit stream and either interpret it or write it to a
tcpdump-style capture file.
I don't know if that type of hardware exists, or how one would
construct it or connect it to a modem or any other such device;
I also don't know of any software that would handle it. I
cannot help you any further on that one.
possibility 2:
It might be possible to plug the computer that is to be
connected to the network into the other computer, and plug
*that* computer into the phone line, and run some kind of
program on the computer in the middle that passes data through
in both directions, saving that traffic to a file.
I don't know of any software that would handle that, and cannot
help you find it or write it, so I cannot help you any further
on that one.
There may be other possibilities as well; I don't know what they are,
offhand, and cannot help you any further.
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