Faxploit: Sending Fax Back to the Dark Ages

https://research.checkpoint.com/sending-fax-back-to-the-dark-ages/

by blopeur • 8 years ago

207 61 8 years ago

research.checkpoint.com

mamurphy• 8 years ago

If this starts showing up in the wild as a new attack vector, it would be great if companies/governments decided to abandon faxes and embrace email attachments as a response. If both are subject to vulnerabilities are there any upsides to continuing to use fax?

peterwwillis6• 8 years ago

The only digital equivalent of a fax is:

1) Get a public IP address on the internet. 2) Put a server on the internet, with an open port, running software that can receive arbitrary files. 3) Connect to it from your computer and send it a file. 4) Receive confirmation that the remote server correctly received your whole file.

Everything else, like e-mail, depends on a chain of service providers and accounts to deliver and store content reliably over the network. Fax enables any person with a phone number to send documents to any person with a phone number. E-mail may seem similar (you need a phone service provider and a fax machine), but I think faxing is a less technically complicated solution, more reliable overall, and allows a lot more independence.

walrus01• 8 years ago

New SaAS VC-funded startup: Netcat As a Service (NaAs). Cloud hosted with slick HTML5 control panel.

losteric• 8 years ago

Everything else, like e-mail, depends on a chain of service providers and accounts to deliver and store content reliably over the network

In your proposal, how do the packets get from point A to B?

varenc• 8 years ago

Doesn't calling a phone number rely on a chain of service providers as well? Your fax probably needs to be bounced through several companies and some of that infrastructure ends up shared with internet infra anyway.

Though I agree that for many end users sending a fax is easier and simpler, but that seems mostly because of experience and familiarity.

nitemice• 8 years ago

Sounds like an FTP server to me.

deathanatos• 8 years ago

It doesn't need to be that equivalent though. Some changes can be / are beneficial.

The last time I had to send a fax was when my back account had fraudulent charges made against it. My now-former bank wanted me to fill out a form — fine — which they would only snail-mail or fax to me.

This form could simply be hosted on their website, as a PDF. In fact, the form I received had something like Z:\BigBankCo_Shared\Docs\Forms\Fraud.docx on the bottom of it, and in the end, I gave them a number of a service that automatically converts faxes into PDFs in emails.

Now, they wanted me to fax (or snail mail) it back. A email with an attachment to a support address, such as fraud-form-returns@bigbank.example.com, would have suffice. Directly, bit for bit equivalent? No. Gets the job done? Yes.

All together, the entire thing was a few simple questions (my info, information about the transactions, and a statement essentially swearing up and down it wasn't my fault) that could also have just been gathered by an HTML form.

(And, I'm not saying these should replace the snail mail/fax; keep them, if there is sufficient demand for them. Which I suspect that once you have an HTML form, there won't be.)

EamonnMR2• 8 years ago

Reliable? Depends on the implementation I guess. If it's competing with a phone line they might not get it. We used fax to communicate with with far flung doctors offices and it was nothing but trouble. The process of sending or receiving a fax often entaled calling back and fourth to ensure that it arrived and re-sending.

Email, on the other hand, always got through.

Animats2• 8 years ago

You can run inbound and outbound SMTP servers yourself, and send email with no forwarding. Nobody does this, but the protocols support it fine.

pasbesoin2• 8 years ago

The last I knew, in the U.S. the fax still carried some legal recognition/privileges that email did not.

For example, your doctor can fax a prescription to the pharmacist. Or a request for records to another doctor. A faxed copy of a signed contract carries some degree of official legal recognition/status (yeah, go figure).

Bog standard email did/does not carry such authority. Maybe closed email interconnects now do. For example, I think our area health care networks (we have 3 big ones, here) now support email requests for some things requiring authorization. But those emails are within their private network, and on private links between their networks where they've agreed to interconnect on such things.

Or they should be... Speaking more generally, I observe at least some doctors and offices emailing all sort of stuff on the public, general Internet, that should actually remain protected.

(One of the reasons I expect the Internet to continue to be de facto locked down by authority (laws and rubber hoses, as opposed to technically complete "solutions"). People, including authority figures, insist upon using it as if it is secure. They have a lot of power, that will end up enforcing "security" through physical power against those who don't "obey the rules".)

yjftsjthsd-h• 8 years ago

I wonder if we could actually get gpg in use here; it's already a tightly regulated, controlled environment, so we might be able to push through actually standardizing on it, and being able to verify that something truly was signed by a doctor and then encrypt it in transit would be really useful.

jessaustin• 8 years ago

Maybe faxes have legal weight, but that's silly because they are easily spoofed. I agree that HIPAA violation via email is common.

pwg• 8 years ago

The last I knew, in the U.S. the fax still carried some legal recognition/privileges that email did not.

Much of this is the direct consequence of fax being carried over the POTS copper telephone network, where there is some belief (not necessarily accurate in today's world) that the link between sender and receiver over a POTS line is free of "men in the middle". Therefore fax is viewed as 'secure' due to this belief.

EamonnMR2• 8 years ago

This is an unfortunate historical accident of fax and paper coming first. They are not subject to the same security rigor that other IT services are. And a recipe for lost health information and poor patient outcomes.

avip• 8 years ago

FWIW the country I live in has a law that forces all public services to accept requests over email. Though the motivation was to stop the well known "send us a fax" customer abuse vector.

rmetzler• 8 years ago

German lawyers use fax, because the receipt shows the recipient has legally received the message. This is not the case with email. Therefor they created a different kind of electronic mail system (De-Mail [0]) they want people to subscribe to, so people can receive legally binding documents in an account they never look into.

I don't have any numbers about monthly active users and other relevant KPIs, but I bet they are really low.

[0] https://en.wikipedia.org/wiki/De-Mail

giovannibajo1• 8 years ago

Italy has been using this mess for more than ten years now: https://en.wikipedia.org/wiki/Certified_email

zaroth• 8 years ago

Using the HP Officejet Pro 6830 all-in-one printer as a test case, we were able to demonstrate the security risk that lies in a modern implementation of the fax protocol. Using nothing but a phone line, we were able to send a fax that could take full control over the printer, and later spread our payload inside the computer network accessible to the printer.

We believe that this security risk should be given special attention by the community, changing the way that modern network architectures treat network printers and fax machines. From now on, a fax machine should be treated as a possible infiltration vector into the corporate network.

This is a great piece of research and a beautiful write up which is extremely accessible to anyone interested in how these attacks are developed.

The twist at the end, of bundling NSA exploits for complete network takeover all starting from a faxed JPEG file with a malformed header, is icing on the cake.

amaccuish• 8 years ago

As some have pointed out, some countries put more legal weight on a fax. That's just not a thing in Estonia, where everything is digitally signed with your ID card, so you either email or upload official documents.

toomanybeersies3• 8 years ago

In New Zealand, you can send practically any legal documents via email. I don't think you even need to have them signed, being sent from your email address counts as signing them. It makes sense really, forging a signature is actually trivial for most legal documents. Nobody ever looks very hard. It would be harder to access my email account and send an email than it would be to forge my signature.

etatoby• 8 years ago

It's a common misconception that sending something "from your email address" requires any degree of accessing your email account. It does not. The visible "From" is transmitted as a regular header and you are free to modify it at will, much like the Subject line.

Some low-level clients make this easier (say, Mutt) but most clients allow you to do so. For instance, all desktop and mobile apps, such as Outlook, Thunderbird and Apple Mail have an Accounts setting screen where you can change your "sender" email address. You can write anything you want in that field.

Online services, such as GMail, require you to have access to the addresses you wish to use as "sender", but they are the exception. Anybody can still use your GMail address as sender in their emails. (Anti-SPAM features such as SPF notwithstanding.)

ehsankia• 8 years ago

I was watching a round table with Ridley Scott the other day where he admitted he still uses fax because it's more secure than e-mail [0]. Does anyone know how valid that claim is?

[0] https://www.youtube.com/watch?v=3_9bdVECQLo&t=20m37s

toomanybeersies3• 8 years ago

Fax isn't encrypted. If you wiretap the line, you can just read off any faxes. Email can be sent over TLS, and the email itself can be encrypted with PGP.

However, superficially, fax is more secure because there are no stored copies (maybe depending on the machine?). There's the original, and the copy that gets printed out on the other end. If you were to fax over a script for a movie, there wouldn't be a copy sitting on a disk on the receiving end, there would only be a printout. That's what Ridley Scott is alluding to in that video.

duxup• 8 years ago

That and who is really taping the line vs..... trying to hack any computer they can for whatever reason.

Seems like fax has fewer folks targeting that system.

Zenst2• 8 years ago

There are secure fax machines that utilise encryption, require ISDN and used by UK government since the 90's (unsure if still used but probable).

exikyut3• 8 years ago

Haha no. Telcos have had a tapping mentality for a long time. It's not advertised, but it's clearly there.

So, if we go from there and then take something like https://theintercept.com/2018/06/25/att-internet-nsa-spy-hub... and consider the complexity of that, then ponder XKEYSCORE and so forth, yes, absolutely ISPs store faxes __precisely because they're unencrypted__ and __precisely because they're routinely used for medical and other sensitive data__.

Or the NSA isn't worth its $1B/yr.

I don't know Ridley Scott, but he needs to talk to a nice security researcher at some point, someone whose feet are on the ground and who likes sharing honestly.

gh2k• 8 years ago

While it would be great if everyone used PGP, I don't think you can guarantee that interim SMTP servers (of which there could be several on your email's path to its recipient) will communicate with each other over TLS, or that your end user will download the email over a secure connection either. So, wiretapping your email is definitely that can happen even if you send it securely.

tehlike• 8 years ago

The same researcher, Eyal Itkin, found a number of vulnerabilities in cryptocurrencies (I am familiar with his Monero ones). Hats off!

Spare_account2• 8 years ago

Forgive me if this self evident or discussed in the article, my head was reeling by the time I got to the end. I'd appreciate if it anyone could confirm that I understand the situation correctly:

1. The buffer overflow identified exists in a JPEG parser that was written by HP from scratch. Therefore this exploit may only apply to the specific models of HP fax that utilise this firmware (and HP have already patched it, so a fix is available).

2. Disabling colour faxes would mitigate the vulnerability. (I've just scanned three years worth of fax logs from our fax server and we've never received a colour fax).

3. These mitigations aside, the principle remains that fax is often present without any kind of security attached directly to the network and thought should be given to isolating fax infrastructure to reduce exposure to exploitation. (Additionally the constant and ongoing lobby to management to permanently retire fax should be maintained).

edent• 8 years ago

1. That someone wrote. Maybe HP got it from an OEM and it is in dozens of manufacturers' machines.

2. Would mitigate this vulnerability. And, the nasty thing about this is that it could potentially rewrite your logs. You can't trust a compromised machine to tell the truth.

3. Yup.

Spare_account2• 8 years ago

Sorry for the late reply. Thank you for taking the time to respond.

tearns• 8 years ago

So has anyone heard whether Dell or Xerox are also facing this vulnerability? Or if either have made a statement?

I've checked Dell's sites for updated firmware but for the models I would need, they haven't released a firmware upgrade since 2016.

Faxploit: Sending Fax Back to the Dark Ages

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