Path: utzoo!utgpu!watmath!clyde!att!chinet!dwtamkin
From: dwtamkin@chinet.chi.il.us (David Tamkin)
Newsgroups: comp.dcom.modems
Subject: Re: About "+++" in-band escapes
Summary: a way around it
Keywords: S2 register escape answer
Message-ID: <7823@chinet.chi.il.us>
Date: 26 Feb 89 17:07:12 GMT
References: <20335@lll-winken.LLNL.GOV> <20736@lll-winken.LLNL.GOV> <3695@phri.UUCP> <17584@onfcanim.UUCP>
Reply-To: dwtamkin@chinet.chi.il.us (David Tamkin)
Distribution: na
Organization: Chinet - Public Access Unix
Lines: 22

In <17584@onfcanim.UUCP> Dave Martindale wrote:

| So, you really need some way of turning off the in-band escape
| sequence for a modem used as an answer modem.  Yet, if the same modem
| is also used for dialout, you can't disable command mode entirely.

If possible, as it is with Hayes-compatibles by writing a new ASCII code to
register S2, pick a different character from decimal 043.  Many modems
don't retain S2 in NVR and you have to rewrite it every time you turn the
modem on, but if you use it for auto-answer you probably don't flip the
power switch too many times in a day.

Yes, a hacker will still be able to try every code from null through rubout
but you won't have the answering modem knocked off line because a caller
was innocently trying to get his or her own modem into command state.

Another suggestion is to disable escaping to command mode when you set up
for auto-answer and to re-enable it when you place an outgoing call.

David W. Tamkin     Post Office Box 567542    Norridge, Illinois  60656-7542
dwtamkin@chinet.chi.il.us         CIS: 73720,1570          GEnie: D.W.TAMKIN
Anyone on Chinet who agrees with me is welcome to speak up on his or her own.