Great Circle Associates Firewalls
(April 1995)
 

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Subject: Re: Re: Secure modem pool
From: ericm @ lne . com (Eric Murray)
Date: Wed, 26 Apr 1995 12:14:30 -0700 (PDT)
To: wegrzyn @ tribble . lkg . dec . com (Chuck Wegrzyn)
Cc: Firewalls @ greatcircle . com
In-reply-to: <9504261506 . AA25732 @ tribble> from "Chuck Wegrzyn" at Apr 26, 95 11:06:35 am

> 
> 
> Please forgive me if I am wrong, but from what I know there is no way
> to simulate a 'hangup' condition by asserting a sound. The telephone
> spec calls for the tip-and-ring voltage to change.

according to an article in '2600' all it calls for is
a switch and a resistor then a sound generator to produce
the two tones that make up a dial tone.

i don't know if that works, not having tried it myself.  however
trying it on say my home CO does not prove that it does or
doesn't work when the prospective hacker calls from a CO with different
switch hardware.  since the time it took me to configure a callback
system to use seperate incoming and outgoing modems was less
than it would have taken me to test the bogus hangup theory, i decided to
go ahead and assume that the theory was correct and protect my
network from people who might use it.


-- 
eric murray     ericm @
 lne .
 com


References:
Indexed By Date Previous: Re: E-mail virus scanning(Good Times)
From: Adam Shostack <adam @ bwh . harvard . edu>
Next: Re: Secure Modem Pool
From: Adam Shostack <adam @ bwh . harvard . edu>
Indexed By Thread Previous: Re: Re: Secure modem pool
From: wegrzyn @ tribble . lkg . dec . com (Chuck Wegrzyn)
Next: Re: Secure Modem Pool
From: Rens Troost <rens @ imsi . com>

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