Mailinglist Archive: opensuse (1108 mails)

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Re: [opensuse] Fax vulnerability
On 2018-08-17 05:18, Bruce Ferrell wrote:
On 08/16/2018 06:21 PM, James Knott wrote:
On 08/16/2018 12:08 PM, Anton Aylward wrote:
Fax is about as secure as a land line.

My GP won't notify me about results, appointments or anything by
e-mail, they
consider email to be 'insecure'.
But I can go to the basement of their building, thee parking ports,
and look at
the wring and clip a recorder on there.  FAX is not secure.
I get the same thing.  In fact, I had the same discussion with my doctor
recently.  People who have little knowledge of telecom and IT have no
idea how insecure it is.  I have worked in telecom and other areas of IT
for decades.  I know how easy it is to tap onto a phone line (I was
doing that as a teenager) and I can also spoof phone numbers (it's
common practice for businesses to display the main number on call
displays), if I get my hands on the equipment.  There are lots of fax
modems kicking around that could easily be modified to intercept faxes.
Also, many years ago, shortly after I got my first fax modem, I faxed
myself a document that had nothing but my signature on it.  I did that
so I could cut 'n paste my signature on documents where they wanted a
signature.  There was nothing to stop me from doing the same with
someone else's signature.

From your perspective, you're correct.... Fax isn't secure.

From others (the courts for example) Fax IS secure and is
accepted/demanded as a legal document.  Email is not... and we all know
for bloody good reason.

Well, they are silly. An email can be cryptographically signed and/or
encrypted, thus both authenticity and privacy can be secured. Fax can
not today address any of that.

For instance, I had my boss signature scanned so that I could fax
documents signed by him - when he told me to do so. It was the only way
to fax a signed document from the computer. The alternative was write it
up in the computer, print, sign, scan with computer, send. There was
some quality loss in the text, so we preferred the other way.

Now, having said all of that I'll address your comment about tapping
onto the line to make a copy of a fax transmission...

I worked in the telecom business for a fairly long time in central
offices and switches.  Yes, you can record the audio tones, but a fax
modem is a VERY fussy beast and that trick tends to not work.

Not saying you can't do it, it's just not as easy as TV and modern
security researchers would have you believe.

Not as easy, but possible. The machine itself has to be silent, can't
negotiate protocols or ask for repeats. Has to know what to do when the
receiving machine talks.

Nor is cracking the ss7 network.  Access is tightly controlled. One does
not "just get on" that network.

If you read the accounts of the researchers doing the security work on
the ss7 network, way down at the bottom, you always see where they thank
some network/access provider for allowing them onto the ss7 network so
they can tell them how they run a crappy network.

That's true, they need access first. It is usually one time slot in a T1
or E1 (MIC?).

I suspect that James was referring to the ISDN signalling channel, which
can be intercepted by wire tapping into the client copper line. This is
not SS7.

By the way, any phone conversation (not VoIp, but traditional) can be
intercepted digitally anywhere in the road, and interception can not be
detected on the ends. It is in fact a computer sending the stream of
bits that forms the conversation to another phone line, which can be
virtual (a file if capacity and software permits). There is no delay
involved, no signal degradation at all - because it is done after the
original signal is digitized.

However, the capability to do this in the switches I worked at was very
limited. It could be done to investigate (debug) problems, not for
police work, and perhaps only half a dozen simultaneous taps. And was
registered in logs. Possibly for legal wiretapping another module was
needed we did not have.

Cheers / Saludos,

Carlos E. R.
(from 42.3 x86_64 "Malachite" at Telcontar)

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