Questions tagged [pdf]

Portable Document Format (PDF) is an open standard for electronic document exchange maintained by the International Organization for Standardization (ISO). Questions can be about PDF specific malware or protections.

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1answer
113 views

Gmail warns about encrypted PDF file

I recently received a PDF file that, when attached to a gmail message, causes a warning to be displayed as follows: Encrypted attachment warning – Be careful with this attachment. This message ...
16
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1answer
30k views

How can I extract the hash inside an encrypted PDF file?

As long as I know, the encrypted PDF files don't store the decryption password within them, but a hash asociated to this password. When auditing security, a good attemp to break PDF files passwords ...
14
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2answers
42k views

How to know if a PDF file is infected?

I'm afraid to open a PDF book. When checking the file via pdfid, I get this: PDF Header:% PDF-1.6 obj 4175 endobj 4174 stream 3379 endstream 3379 xref 0 trailer 0 startxref 1 /...
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1answer
75 views

How can a pdf file have two passwords?

I receive emails from my bank with password protected PDF files, and they provide two passwords - either xxxx or yyyy. How is this possible?
19
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3answers
27k views

How can I tell if a PDF file I was sent contains malware?

I was emailed a PDF file by a family member. I have reason to suspect that it was given to said family member by someone who would like nothing more than to infect me with a Remote Access Trojan. How ...
3
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1answer
120 views

Can a PDF embed a tracking image?

I know that PDFs can contain embedded images and Javascript. Can a PDF contain something that tracks you? For instance, can it contain a remote image that, when the PDF is opened, will fetch that ...
2
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1answer
107 views

Why do PDFs contain password hashes?

Reading this question about extracting PDF password hashes to feed into john the ripper has me wondering why password hashes are in a PDF in the first place? Shouldn't it be using the supplied ...
0
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1answer
114 views

Risks of allowing users to upload PDF and XML files to be stored/retrieved from a DB (ASPNET MVC 5)

I'm modifying an ASPNET MVC 5 web site and a requirement is to allow users to upload an XML and PDF file. The XML file will be used to layout text on the PDF based on variables coming from within the ...
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0answers
23 views

How to make PDF-file post data on load?

I've been trying to create a .pdf file via msfconsole that would open cmd on a windows device and curl POST data to a server. I've previously checked this link and found the following: se exploit/...
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0answers
35 views

John the Ripper [duplicate]

I've already cracked a PDF with pdf2john but it doesn't show the password. What could be the problem? (The password isn't blank.)
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0answers
128 views

Android 10 downloaded suspicious files without my permission

This is my first question on this forum so please let me know if I need to clarify anything. My Android 10 Pixel 2 just downloaded 2 files without my permission today, both named something to the ...
68
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3answers
232k views

Can a PDF file contain a virus?

Could a PDF file contain any type of malware?
6
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5answers
468 views

Document security - how to find who's leaked a confidential document?

I am legally obliged to distribute a document (probably by email, probably saved as MS word, or a PDF) to several hundred recipients. The recipients are legally obliged to keep it confidential. ...
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1answer
79 views

PDF User Password always give access to the Owner Password, even when encrypted with AES-128

I've been messing around with qpdf, and noticed something that seems huge: that a document's Owner Password is essentially useless, as it can be easily unset, and therefore that only the User Password ...
2
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1answer
61 views

PDF Server Side 2020

I have been gathering information on handling PDF files for web applications. Much of my research has been on displaying the files to the user. What I want to learn here is how to properly handle the ...
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0answers
54 views

PDF Documents - Browser View 2020

I posted a question yesterday about PDF files in a browser that can be found here. There you can find more information about dealing with PDF documents in browser. My question here is how each ...
3
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1answer
142 views

PDF Documents in Browser 2020

I have a project where I would like to allow a user to view a document (PDF) in their browser by clicking on a link or thumbnail of the file. They would be able to download said file. Ive just begun ...
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4answers
6k views

How to detect malicious JavaScript in a PDF file?

Is having any JavaScript in a PDF file by definition dangerous or is it only dangerous when specific functions (for example eval) are used inside a PDF, in which case, what JavaScript functions are ...
10
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1answer
5k views

What are the security risks associated with PDF files?

What are the security risks associated with PDF files? There is, of course, the general risk associated with any type of file: that whatever application is used to read it will have a bug that can be ...
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0answers
25 views

Can flattened pdf documents contain viruses? [duplicate]

While I came to this site from researching whether inactive (or flattened) PDF documents could contain viruses and have come across this link in this site, it does not answer my question. I need to ...
6
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1answer
99 views

Printing document on usb drive with confidential information on multi user computer

I have a pdf file with confidential information on a usb flash drive. This document needs to be printed on a multi user Ubuntu system. I want to prevent other users from seeing the content of the ...
3
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1answer
952 views

How can we embed an exe containing a payload into a pdf file [closed]

I have created an exe with a payload which gives me a meterpreter session. But I need to embed this exe into a pdf. Upon opening the pdf the exe ideally should get executed. Is there any way to do ...
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0answers
58 views

Safest way to open PDFs on Android and iOS?

I was checking out Qubes' way of creating safe PDFs, but unless you use Qubes as a daily driver (and use DispVMs to open PDFs) it's still not viable to just use it to create image-based PDFs if you ...
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1answer
123 views

How likely are Evince, XReader or Adobe Reader with scripts disabled, to be exploited by a malicious file?

PDFs are very commonly found on the web, and I carefully either view them on the browsers, or use readers without the capability to run the scripts that may come with them (shitty design choice) like ...
43
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5answers
59k views

How to scan a PDF for malware? [closed]

Can anyone suggest an automated tool to scan a PDF file to determine whether it might contain malware or other "bad stuff"? Or, alternatively, assigns a risk level to the PDF? I would prefer a free ...
5
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1answer
109 views

Could PDF's `/Filespec` type allow for remote file access?

I've read the PDF 1.7 spec 7.11.1 (okay, not all the spec, but a part of it), and I've seen that you have what Adobe calls /Filespec type objects. As far as I get it, this means that a PDF can make a ...
2
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1answer
11k views

PDF UrlMal-inf[Trj] Virus

When I create PDF file from my particular DOCX file, it gets infected with the virus. But if I create a new DOCX file and create PDF from that, it doesn't get infected with the virus. I have tried ...
4
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1answer
283 views

Can the conversion of a malicious PDF to image be exploitable?

Let's say I want to allow to the customer's of my website to upload PDF documents. What would be more safe to do: Convert the PDF to image using a library and store it in my file server as an image? ...
5
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4answers
1k views

Remove pdf malware by re-printing to new pdf or text extract?

Consider you have a suspicious pdf file that might contain malware. Would it be sufficient to either: open the pdf file in a virtual environment and let the pdf viewer or pdf-creator program "print-...
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2answers
2k views

Why is PDF still safe?

Something I was wondering about after reading Didier Stevens Labs 2008 post: There are endless ways described how to put potential malicious content into a pdf file, while making it impossible for ...
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3answers
240 views

Reading potentially hidden properties of a PDF file

I have a PDF file which, when going via "Properties", shows no data. For example, no mention of the author of the file. Is there any way I can unlock such information?
4
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1answer
2k views

Why won't pdf2john extract the password hash of this encrypted pdf? Getting blank results

New to the community, and to JtR and Hashcat as a whole, but after searching for a few days I couldn't find a solution to this specific problem. I have a password protected PDF file that I'm trying ...
2
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1answer
161 views

How can I detect and reject potentially unsafe pdf uploads

We develop a web app that will start accepting pdf uploads, which will be stored and distributed to other users. Pdfs seem remarkably unsafe still. How can I scan and reject any pdf that does ...
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1answer
155 views

Reason for fake academic pdf files found on sites like Google Scholar? [closed]

Using my web-browser, I clicked a link on Google Scholar that led to a fake paper (in .pdf format). The pdf contained many keywords and phrases related to the research topic, possibly for search ...
3
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2answers
361 views

Hash value changes after first opening a file

Is it possible or normal that the hash value of a file changes just after the first opening/execution of it? I used sha256sum function within Ubuntu terminal to check the hash values before and after ...
1
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1answer
755 views

Some digitally signed pdfs shown as verified in the pdf viewers while others are not [closed]

I have two pdf documents: 1 - My class 10 marksheet issued by the CISCE that I downloaded through digilocker. 2 - My Domicile certificate issued and downloaded from the aaplesarkar website. Both ...
2
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1answer
200 views

Is it safe to view local pdf files in a browser?

When receiving a pdf file by e-mail, the question is how to open it. Browsers are normally quite secure, don't support all pdf features (an advantage in this case) and the viewer/conversion might ...
3
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0answers
57 views

Burst and rebuild pdf to discard eventual embedded malware

This question deals with how to scan, while i am curious if my acrobat reader DC is compromised but in an isolated container and i pull out the pdf. Is it safe to disassemble the pdf by pdftk burst .. ...
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0answers
460 views

What is the difference between PKCS#7 and CADES, PADES and XADES?

I am newbie in PKI. For signing a pdf documents we are free to consider each pkcs#7 format or PADES format. If I have some misunderstandings, please turn it on for me.
3
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1answer
1k views

Send GET request from a PDF file

I'm currently working on a security Proof Of Concept where I need to show the danger of opening an unknown PDF file. Internet says that many malwares use Javascript in PDF document (AcroJS) to ...
2
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0answers
231 views

What encryption method is used on macOS Preview.app?

In order to send a file securely, I am going to encrypt/password protect a PDF file with Preview on macOS. Other question(s), such as this one have asked the method of encryption for PDF's in ...
10
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3answers
4k views

Can you directly view a malicious PDF on Linux?

There have been questions on safe viewing of malicious PDFs on OS. I would like to know if it's okay to directly open them to view them in a Linux OS because the OS is said to be secure and malware-...
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1answer
48 views

Does making a pdf searchable make it more vulnerable? [closed]

I would like to know if making a pdf 'searchable' somehow make it less secure?
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0answers
26 views

How secure is pdf password protection? [duplicate]

I'm assuming PDF password protection uses encryption. How secure are the methods used? Can it be easily cracked or is it more in line with modern GPG encryption in terms of strength?
4
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2answers
3k views

Malicious PDF file upload

I have a web server for my customers to upload their PDF files. I have also an IDS/IPS with Anti-Malware license that is between the user and the web server and blocks malicious PDF files from ...
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0answers
42 views

What source formats are affected by ImageMagick's vulnaribility caused by Ghostscript?

According to https://www.theregister.co.uk/2018/08/23/imagemagick_ghostscript/ ImageMagick's convertion to PDF of arbitrary (user-submitted) documents should not be used because of Ghostscript's ...
3
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1answer
2k views

PDF and embedded JavaScript

We have completed a vulnerability and a penetration test. One feature of our application allows for documents to be uploaded, and we allow for PDF documents. Prior to a document being accepted we ...
1
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2answers
5k views

Is this a safe way to open a PDF file? [duplicate]

I have recieved an email with a pdf file whose content I want, but I'm not exactly sure what the source of it is. In gmail, I have two options: "Download" and "Save to Drive". I'm assuming it means ...
3
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1answer
91 views

What is the industry standard practice for saving a potentially (likely) malicious PDF for analysis?

I've received an email with an attached PDF which has many signs of being a malicious attachment. Lacking the time and resources to analyze it at the moment, I'd like to store it for later use, and ...
1
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1answer
106 views

How useful is PDF signing in real world usage?

Background senario: So we had a problem where our system (Alice's shiny widgets) generated a PDF with a quote amount for 10 widgets. Someone (Eve) took the PDF, altered it to increase the price by 20%,...