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RE: Ancient Trivia: +++ath0
From: "Cowles, Robert D." <rdc () slac stanford edu>
Date: Wed, 17 Mar 2004 19:11:10 -0800

The version I heard went something like:

Hayes implemented a "guard" ... they required a pause
between the "+++" and the following command. When
other manufacturers implemented the command set,
they had to make some small changes so they could
claim they hadn't *completely* ripped off the Hayes
command set ... they left out the requirement for 
the pause.  So, on lots of non-Hayes modems, you could
get them to hang up by just sending that string as data
(or including it as data in a ping packet).

Bob Cowles

-----Original Message-----
From: psz () maths usyd edu au [mailto:psz () maths usyd edu au] 
Sent: Wednesday, March 17, 2004 6:17 PM
To: full-disclosure () lists netsys com; lscharf () aoe vt edu
Subject: Re: [Full-disclosure] Ancient Trivia: +++ath0

Luke Scharf <lscharf () aoe vt edu> wrote:

As the old BBS'ers and even older folks know, the string 
"+++ath0" will
disconnect a modem. ...
Does anyone know what versions of windows had this 
particular bug in the
PPP implementation?  Were any other systems affected?

I guess that the problem is not so much an issue in PPP (on 
the client PC
or at the ISP server), but the settings of both modems. To 
fix, you need

  +++ats2=255

on both: see e.g.

  
http://www.tldp.org/HOWTO/Remote-Serial-Console-HOWTO/modem-ha
yes.html#MODEM-HAYES-ATTENTION

for details. (Also, there was a discussion on BugTraq at the end of
September 1998, maybe it would be useful to look in the archives?)

Cheers,

Paul Szabo - psz () maths usyd edu au  
http://www.maths.usyd.edu.au:8000/u/psz/
School of Mathematics and Statistics  University of Sydney   
2006  Australia

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Charter: http://lists.netsys.com/full-disclosure-charter.html


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