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GPEN · Question #325

You work as a Network Administrator in the Secure Inc. You often need to send PDF documents that contain secret information, such as, client password, their credit card details, email passwords, etc.

The correct answer is C. PDF passwords can easily be cracked by brute force attacks.. Password-protected PDFs offer weak security because the PDF password encryption is vulnerable to brute force attacks, allowing attackers who intercept the file to crack it offline without a time limit.

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Question

You work as a Network Administrator in the Secure Inc. You often need to send PDF documents that contain secret information, such as, client password, their credit card details, email passwords, etc. through email to your customers. However, you are making PDFs password protected you are getting complaints from customers that their secret information is being misused. When you analyze this complaint you get that however you are applying the passwords on PDFs, they are not providing the maximum protection. What may be the cause of this security hole?

Options

  • APDFs can be read easily in the plain-text form by applying a sniffer.
  • BPDFs are sent in email in the plain-text form.
  • CPDF passwords can easily be cracked by brute force attacks.
  • DYou are applying easily guessed passwords.

How the community answered

(26 responses)
  • A
    8% (2)
  • B
    4% (1)
  • C
    85% (22)
  • D
    4% (1)

Why each option

Password-protected PDFs offer weak security because the PDF password encryption is vulnerable to brute force attacks, allowing attackers who intercept the file to crack it offline without a time limit.

APDFs can be read easily in the plain-text form by applying a sniffer.

PDFs are a binary file format, not plain-text, so a sniffer captures the binary attachment rather than directly readable content.

BPDFs are sent in email in the plain-text form.

While email may transmit the PDF as a base64-encoded attachment, the scenario concerns the protection applied to the PDF file itself, not the encoding of the transport layer.

CPDF passwords can easily be cracked by brute force attacks.Correct

PDF encryption (historically RC4, and even AES in older standards) can be attacked offline using brute force or dictionary attack tools such as hashcat or dedicated PDF crackers once the file is intercepted. Because the attacker has unlimited time and no lockout mechanism, even moderately complex passwords can eventually be recovered, making password-only PDF protection insufficient for transmitting highly sensitive data.

DYou are applying easily guessed passwords.

Easily guessed passwords are a contributing user-behavior risk, but the core security hole described is that brute force tools can crack any PDF password - strong or weak - given enough time.

Concept tested: PDF password encryption vulnerability to brute force attacks

Source: https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-111.pdf

Topics

#brute force attacks#password cracking#PDF security#encryption weaknesses

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