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That is, can they send any personally identifiable information to an external host (for example, the PDF author's server)? If so, is there a way to disable this in common PDF viewers (Adobe Reader, Mac OS X Preview) without resorting to using a firewall rule?

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6 Answers 6

the documents don't, certain applications to open them (e.g. Adobe Reader) do have the capability to phone home (the software maker, not the author of the document, that is). they can be "silenced" with outbound firewall rules.

Adobe Reader is also plagued by a variety of security vulnerabilities, that can be triggered by documents and should not be taken lightly.

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They are certainly not supposed to be able to except perhaps to report result from a form submission, but there's a Javascript engine in recent Adobe PDF implementations that has been the source of security problems with Acrobat Reader and related software.

Adobe's docs on the Javascript API for Acrobat products may give you some ideas about hat it's supposed to do and are easily found (sorry for not linking, low rep here).

Here is one of the many posts to SANS ISC about Acrobat Reader vulnerabilites related to the Javascript feature. Please be aware that even when disabled as recommended the Javascript feature is often re-enabled by Adobe software updates. There's a lot more discussion on the various security sites about this if you'd care to look into it.

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welcome to superuser. i had the same problem my first few posts. if you have extra links you can always add them in comments to your posts. –  quack quixote Oct 4 '09 at 1:03

I don't know how it works, but somewhere in 2002 I used Adobe Reader to fill in an offline PDF tax-paper. Upon pressing a button within that PDF form, it prompted for my password, encrypted itself, connected to the internet, and sent itself (or its data) to the tax-collector's office. It then told me the password was actually wrong, and had me repeat the steps.

So, assuming pressing a button is not really required to do this, I guess any PDF document that is actually a form can phone home when opened in a capable reader.

Also, some read-only PDF forms actually always fetch the data they show from the internet. I have had some digital bills sent to me through email, which would open fine when I got them. However, some time later after the web shop had changed their web site, the bills showed up empty when I opened them again.

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As others have pointed out, Acrobat Reader provides scripting capability within PDF documents. You should check the configuration options in your default PDF viewer and disable any suspicious options. (For me, I can't think of any reason for Reader to need Javascript, or open other programs, so I disable that in the options.)

I haven't tried any recent versions of Reader, but my latest version (Reader 6.0) installed with many many plugins that slowed down the program's startup. Many of these plugins are how forms and scripting functionality are supplied.

You can control which plugins start by moving them out of Reader's plugin directory. For me, that's

 C:\Program Files\Adobe\Acrobat 6.0\Reader\plug_ins

You should make a folder, say, at

 C:\Program Files\Adobe\Acrobat 6.0\Reader\plug_ins_old

and move any unwanted plugins to that directory. I got a nice speedy program start by moving all the plugins into plug_ins_old except for these:

EWH32.api
Search.api
Search5.api
eBook.api
printme.api

Most people will be using more recent versions of Reader, so I imagine the process may be a little different, but that may be a good place to start looking. If Reader stops opening after you've moved a plugin, just move it back and re-try.

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Depends on your definition of ‘personally identifiable’. Scripts in PDF don't have any particular way to gather information on their own, but they can certainly connect to the network (through SOAP or scripted form submission) and upload any information you put into them (along with your IP address, of course).

If you have a DRM-protected PDF the authorisation process will also necessarily upload a unique ID for your installation and file.

I can't confirm whether any of these processes can happen without a prompt, because I only use PDF readers that don't support script and DRM. Back when I still used Acrobat I always used to disable JavaScript and delete the plugins as suggested by ~quack.

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Try ditching Adobe Reader and using FoxIt Reader. May not remove this problem but is much less bloated piece of software and launches nice and quickly and it's FREE

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