RE: Vulnerability testing in analog modem

["Craig Wright" <Craig.Wright () bdo com au>]

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
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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.