TELECOM Digest OnLine - Sorted: Re: 'Phone Tapping' Modem Traffic ?

Re: 'Phone Tapping' Modem Traffic ?

John Levine (johnl@iecc.com)
13 Jun 2005 18:47:31 -0000

>> How difficult is it for them to 'decode' my modem [to ISP] traffic ?

On modern modems at 9600 bps and up it's fairly hard. The traffic in
both directions uses the full bandwidth, and each end does echo
cancellation, subtracting out a time-delayed copy of what it sent, to
recover the other end's signal. If you're sniffing in the middle
without a copy of what's been sent from either end, I suppose it's
possible with a sufficiently sophisticated signal processor, but it's
not something you could do by plugging in an off the shelf modem and
tweaking settings like you could do at 1200 bps.

R's,

John

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