A password hash database has been exfiltrated from a company. The hashes are unsalted MD5. The security team wants to quickly identify which users have weak passwords. Which attack would be most efficient for this purpose?

Use a rainbow table to reverse the hashes directly.

Use a dictionary attack with a list of common passwords, hashing each and comparing to the database.

Use a brute-force attack trying all possible character combinations up to 10 characters.

Use a side-channel attack to measure the timing of hash comparisons.

A software developer is using a hash function to verify file integrity. The security team warns that the hash function is vulnerable to a birthday attack. What is the primary risk associated with this vulnerability?

An attacker can perform a dictionary attack to guess the file content.

An attacker can reverse the hash to recover the original file content.

An attacker can find two different files that produce the same hash, allowing substitution of a malicious file.

An attacker can brute-force the hash to find the key used in the hash.

How can an attacker use a known plaintext-ciphertext pair?

To directly read the plaintext of the known message

To derive the encryption key or decrypt other messages

To perform a denial-of-service attack

Which countermeasure is most effective at defeating rainbow table attacks?

Encrypting the hash with a secret key

Adding a unique salt to each password before hashing

EC-CouncilCertified Ethical Hacker

Domain 9Objective 3

Cryptanalysis and Attacks CEH Practice Questions (Page 9)

Part of the Cryptography domain, which makes up ~9% of our current practice bank. EC-Council does not publish an official question count, but from its 240-minute exam (~95–160 total, ~9–14 in this domain), expect 2–4 from this objective — we provide 63 practice questions to prepare you well beyond it. (estimate)

63questions here

13free pages

16concepts

16 Concepts in This Objective

Cryptanalysis Fundamentals
Types of Cryptanalytic Attacks
Brute-Force Attack
Dictionary Attack
Rainbow Table Attack
Frequency Analysis
Known-Plaintext Attack
Chosen-Plaintext Attack
Chosen-Ciphertext Attack
Related-Key Attack
Side-Channel Attacks
Man-in-the-Middle Attack
Replay Attack
Birthday Attack
Meet-in-the-Middle Attack
Cryptanalytic Tools and Techniques

Questions 41–45

41application · medium
A password hash database has been exfiltrated from a company. The hashes are unsalted MD5. The security team wants to quickly identify which users have weak passwords. Which attack would be most efficient for this purpose?
Select an answer first
42application · medium
A penetration tester is using a tool to crack password hashes obtained from a Windows system. The hashes are NTLM hashes, and the tester has a wordlist of common passwords. The tester also wants to apply rule-based transformations to the wordlist (e.g., appending numbers, capitalizing). Which tool is most appropriate for this task?
Select an answer first
43application · medium
A software developer is using a hash function to verify file integrity. The security team warns that the hash function is vulnerable to a birthday attack. What is the primary risk associated with this vulnerability?
Select an answer first
44foundation · easy
How can an attacker use a known plaintext-ciphertext pair?
Select an answer first
45foundation · easy
Which countermeasure is most effective at defeating rainbow table attacks?
Select an answer first

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