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RE: Vulnerability testing in analog modem
From: "Craig Wright" <Craig.Wright () bdo com au>
Date: Sat, 27 Oct 2007 05:55:19 +1000

Some modems (most actually these days) have a Fax capability, However, most Fax machines do not have a modem function. 
A modem is not a fax and visa versa.

 There is no currently known means to compromise a Fax machine and get onto a network. There is no theoretical scenario 
where this is possible that has been proposed.

You can not bridge a network over the fax protocols. You could create a device that would do this, but it would be 
needed on each end and would be in effect a modem taking the analogue fax signal and changing it to a digital 
connection and back.

So what this comes to is are you testing modems - which can be used to create a link or faxes? A modem bank used as a 
fax service is NOT a fax machine.

When connected to a FAX machine over the fax protocol, there is no bridge. It is an analogue signal and is never 
converted into any networked protocol. Faxes do not work like modems.

 So to conclude, there is no test as you never make a connection to a fax machine in the manner that you suspect.

What you are suggesting is that you can get a modem connection (if the fax machine is not a fax machine, but a modem 
simulating a fax). Even this is incredibly difficult if the device is set as a fax alone.


Craig Wright


Craig Wright
Manager of Information Systems

Direct : +61 2 9286 5497
Craig.Wright () bdo com au
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BDO Kendalls (NSW)
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From: listbounce () securityfocus com on behalf of firstkhan2000 () yahoo com
Sent: Fri 26/10/2007 11:49 PM
To: security-basics () securityfocus com
Subject: Vulnerability testing in analog modem

All of us know that a fax machine should not be on a corporate network because it has dial in/out capability on one 
side and connected to the NW on the other - thus, creating a bridge to the NW thru the insecure modem connection. As a 
security person, I would like to test it by dialing into the fax machine, and thru the established bridge, enter into 
the network, and see what's the exposure.

What would be the best way to conduct this test? I would be grateful if someone could point me to a step by step 
testing situation/document.

Best Regards,

First Khan

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