From: chuck gelm <chuck@gelm.net>
To: Jim Nelson <james4765@verizon.net>
Cc: linux-newbie@vger.kernel.org
Subject: Re: tcpdump: How do I filter 'bootp' packets?
Date: Wed, 08 Dec 2004 17:56:22 -0500 [thread overview]
Message-ID: <41B78696.7000500@gelm.net> (raw)
In-Reply-To: <41B77BE5.6000001@verizon.net>
Jim Nelson wrote:
> chuck gelm wrote:
>
>> Howdy:
>>
>> I have cable modem access to the internet now and the download speed is
>> double my original DSL speed. :-) However, I am concerned about
>> security.
>>
>> Can other cable modem subscribers see my packets?
>>
>
> IIRC, most modern cable modems filter anything not addressed to them -
> you'd have to hack your modem to get it to go into promiscuous mode.
>
> It's not easy to do, and it relies on brain-dead network admins to leave
> some back doors in.
>
> OTOH, you could probably find hardware to do just this - if you were in
> law enforcement.
>
>> To test this, I am trying to use tcpdump to monitor packets that my
>> cable modem is sending to my 'router'.
>>
>> I am using these arguments:
>> tcpdump -i eth1 -c 9 -nt not arp and not host W.X.Y.Z > \
>> http://gelm.net/tcpdump.txt
>>
>>
>> (<W.X.Y.Z> == My assigned IP address)
>>
>> I am still seeing many 'bootp' packets.
>>
>> How do filter out 'bootp' packets with tcpdump?
>>
>> Regards, Chuck
Hi, Jim:
I am filtering 'my ip', port 67, and 'arp' and, for several minutes
now, tcpdump has displayed zero packets. So, I seems that...
It would require special hardware for others to view my packets.
I wanted to be sure that it wouldn't be easy.
Regards, Chuck
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prev parent reply other threads:[~2004-12-08 22:56 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-08 2:26 right form for sources.list entries James Miller
2004-12-08 2:41 ` J.
2004-12-08 3:59 ` James Miller
2004-12-08 6:27 ` Ray Olszewski
2004-12-08 13:13 ` tcpdump: How do I filter 'bootp' packets? chuck gelm
2004-12-08 15:50 ` Ray Olszewski
2004-12-08 22:10 ` Jim Nelson
2004-12-08 22:56 ` chuck gelm [this message]
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