Sorry to burst your bubble, but a fax is not a data modem. As I stated in a
prior post, most modems have a fax capability, but not all faxes are modems.
Accessing a modem is possible, but not a fax in the manner you detail. You are
stating an attack against modem strings, but faxes do not have these (not AT
commands though).
Caller ID Commands
· #CID=0 Disable Caller ID
· #CID=1 Enable Caller ID with formatted presentation
· #CID=2 Enable Caller ID with unformatted presentation
Fax Class 1 Commands
· +FCLASS=n Service class
· +FAE=n Data/fax auto answer
Fax Class 2 Commands
· +FCLASS=n Service class
· +FAA=n Adaptive answer
· +FCLASS= Service class
· +FCR= Capability to receive
· +FDCC= DCE capabilities parameters
· +FDIS= Current sessions parameters
· +FPTS= Page transfer status
· +FREV? Identify revision
Etc for Class 3 and up (even Group 4 where the characteristics and operation of
the facsimile devices conforms to the ITU-T recommendations T.563, T.503,
T.521, T.6, T.62, T.70, T.72, T.411 to T.417.).
For a Fax machine you have support of the following:
* Facsimile protocol layer (T.30 with ECM/BFT)
* Facsimile service class 1 command sets (T.31 and EIA-578)
* Facsimile service class 2 command sets (T.32, EIA-592 and industry
standard fax class 2).
* Group 3 facsimile modulations (V.17/V.29/V.27ter/V.21 channel 2).
T.30 has session control and negotiation, but this is not linked to any
protocol support and at best a stack or heap attack will result in crashing the
firmware.
Have a look at -
ITU-T (CCITT) Recommendation T.4. Standardization of Group 3 Facsimile
Terminals for Document Transmission, July 1996
ITU-T (CCITT) Recommendation T.30. Procedures for Document Facsimile
Transmission in the General Switched Telephone Network, July 1996. And
http://tools.ietf.org/html/draft-ietf-fax-tiff-00
On the other hand a T.38 gateway will be connected to the IP network. For the
Ethernet side this is clearly vulnerable to attack. It can not be accessed
using the T.30 protocol over PSTN or even ISDN though. So although this may be
attached over IP, it is still not a fax based attack.
Using Wiki is your biggest issue in your response John. The quote is from
http://en.wikipedia.org/wiki/Fax <http://en.wikipedia.org/wiki/Fax> and it is
wrong - like many Wiki articles. It is simple and close to truth, but not
there. Just because most people believe the world is flat does not make it so.
The issue of a Wiki's fault.
If you read one of the many patients for fax/modems you see details of "fax
detectors". These switch from digital data modes to a fax processing mode as
such:
"The fax detector operates by detecting a known pattern that is present at the
beginning of every fax call. During the initiation of a fax call, certain
parameters are negotiated between the transmitting and the receiving fax
machines. These parameters are transmitted as BFSK signals consisting of a
preamble followed by the parameter data. The preamble is the known pattern
which can be detected. Energy is measured in both frequencies of the BFSK
signals. A decision is made by analyzing these energies and locating a specific
pattern which repeats itself a sufficient number of times." (Qualcomm No.
266521 filed on 1999-03-11)
So, no breaking from the fax to the Ethernet.
A simple test of this is to dial a fax with a war dialer. There is no AT
command to compromise, so the attack referenced will not work.
Regards,
Craig Wright (GSE-Compliance)
Craig Wright
Manager of Information Systems
Direct : +61 2 9286 5497
Craig.Wright@bdo.com.au
+61 417 683 914
BDO Kendalls (NSW)
Level 19, 2 Market Street Sydney NSW 2000
GPO BOX 2551 Sydney NSW 2001
Fax +61 2 9993 9497
www.bdo.com.au
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________________________________
From: jfvanmeter@comcast.net [mailto:jfvanmeter@comcast.net]
Sent: Tue 30/10/2007 6:10 PM
To: Craig Wright; rohnskii@gmail.com; security-basics@securityfocus.com
Subject: RE: Vulnerability testing in analog modem
Hello Craig, A "fax machine" usually consists of an image scanner, a modem, and
a printer combined into a single package.
I seam to remember back in the late 90s, there was a way to gain tech support
remote access to the modem via the Hayes Modem AT strings. It was something
similar to the &T command. Maybe it twas &T2
&Tn - Test and diagnostics; 0=End current test; 1=Start local analog loop back
test; 2=Unknown; 3=Start local digital loop back test 4=Grant remote request
for remote digital loop back test; 5=Deny remote request for remote digital
loop back test; 6=Start remote digital loop back test; 7=Start remote digital
loop back test with self-test; 8=Start local analog loop back test with
self-test.
Take Care and Have Fun --John
-------------- Original message ----------------------
From: "Craig Wright" <Craig.Wright@bdo.com.au>
As for point 1 - what is there to try. A fax is not a modem. There is no
known (even in theory) attack against a fax to gain access.
Regards,
Craig Wright (GSE-Compliance)
Craig Wright
Manager of Information Systems
Direct : +61 2 9286 5497
Craig.Wright@bdo.com.au
+61 417 683 914
BDO Kendalls (NSW)
Level 19, 2 Market Street Sydney NSW 2000
GPO BOX 2551 Sydney NSW 2001
Fax +61 2 9993 9497
www.bdo.com.au
Liability limited by a scheme approved under Professional Standards
Legislation
in respect of matters arising within those States and Territories of Australia
where such legislation exists.
The information in this email and any attachments is confidential. If you are
not the named addressee you must not read, print, copy, distribute, or use in
any way this transmission or any information it contains. If you have
received
this message in error, please notify the sender by return email, destroy all
copies and delete it from your system.
Any views expressed in this message are those of the individual sender and not
necessarily endorsed by BDO Kendalls. You may not rely on this message as
advice unless subsequently confirmed by fax or letter signed by a Partner or
Director of BDO Kendalls. It is your responsibility to scan this
communication
and any files attached for computer viruses and other defects. BDO Kendalls
does not accept liability for any loss or damage however caused which may
result
from this communication or any files attached. A full version of the BDO
Kendalls disclaimer, and our Privacy statement, can be found on the BDO
Kendalls
website at http://www.bdo.com.au or by emailing administrator@bdo.com.au.
BDO Kendalls is a national association of separate partnerships and entities.
-----Original Message-----
From: listbounce@securityfocus.com [mailto:listbounce@securityfocus.com]
On Behalf Of jfvanmeter@comcast.net
Sent: Tuesday, 30 October 2007 3:21 AM
To: rohnskii@gmail.com; security-basics@securityfocus.com
Subject: Re: Vulnerability testing in analog modem
I had a similar pen test, it was on a xerox docucentra, I had several
concerns with the multifunction printer
1. there was/is no auditing of the fax connection, so I could try and
try and no one would never know about the attack.
2. the printer also had a web server, so I copied some test file to the
hd and set up my very own web site.
i believe it is possible to break out of the modem connection, via some
type of diagnotic route and get access to the network.
I recommend that to my client that they configure the phone jack for
outgoing calls only., turn off the web server, set passwords, etc.
I would be interested in hearing anyones thoughts about this. I have a
test coming up for a client on a multi function printer
Take Care and Have Fun --John
-------------- Original message ----------------------
From: rohnskii@gmail.com
I don't know about connecting through the fax to the network but there
is
another security concern to think about.
Fax machines, and printers, that have an internal HD for document
storage can be
a security concern. When the machine is sent out for servicing or
retired there
may be retrievable document images with confidential information on
them.
