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

Re: 'Phone Tapping' Modem Traffic ?

John Levine (
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.



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