The + + + AT Modem Patch
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From: Peter Langston <psl>
Date: Wed, 7 Oct 98 17:19:18 -0700
Subject: The + + + AT Modem Patch
From: Oliver Xymoron <email@example.com>
Subject: Re: 1+2=3, + + + A T H 0 =Old school DoS (fwd)
Oliver Xymoron <firstname.lastname@example.org> has put together a web page that uses
an idea from Adrian Gonzalez <agonzale@NLAREDO.GLOBALPC.NET> to exploit a
frailty of many existing modems. Actually, it exploits the frailty in the
process of fixing it -- it remotely sends and installs a modem "patch" that
disallows further remote control of the modem.
Readers of the bugtraq http://www.geek-girl.com/bugtraq/index.html
mailing list have discussed (at length) the observation that many modems use
the Hayes command set (which includes gaining control of the modem by sending
three plus signs followed by a pause) except they don't require the pause
since Hayes has a patent on using a guard timer to detect the required pause.
The upshot is that a sequence like "+ + + A T H 0" (without the space
characters) will make such a modem hang up the phone line.
Adrian's idea (see http://geek-girl.com/bugtraq/1998_3/0931.html) was to
use the bug to patch the modem by sending "+ + + A T S 2 = 2 5 5 & W O 1 <CR>"
which grabs control of the modem, disables the "+ + +" feature, and puts the
modem back on-line (if the phone line hasn't dropped already).
Oliver's idea was to make a web page to squirt this bug patch through
your modem. To do that, go to http://www.waste.org/~oxymoron/pingpatch.cgi
and click the "Ping me!" button.
-=[ P. Langston - email@example.com - http://www.Langston.com/ - Seattle, WA ]=-
© 1998 Peter Langston