Quick Answer
The correct answer is a dictionary attack. This is because the attacker is using a predefined list of common usernames and passwords—a dictionary—rather than systematically trying every possible character combination. In a brute force attack, the attacker would exhaustively test all alphanumeric permutations, which is far slower and more resource-intensive. On the Certified Ethical Hacker CEH exam, this distinction tests your understanding of attack efficiency and methodology; a common trap is confusing the two when the question mentions “repeated attempts” without specifying the use of a wordlist. Remember the key difference: a dictionary attack relies on likely guesses from a list, while a brute force attack tries every possible key. A simple memory tip is “dictionary = list, brute force = all.”
This CEH practice question tests your understanding of enumeration and system hacking. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A security administrator notices repeated failed login attempts from a single IP address targeting the SSH service. The attempts use common usernames (root, admin, test) and a list of passwords from a dictionary. What type of password attack is being conducted?
Rainbow table attack
Why wrong: Rainbow tables are used offline against hashes, not online login attempts.
Dictionary attack
Using a list of common passwords against usernames is a dictionary attack.
Hybrid attack
Why wrong: Hybrid attacks combine dictionary words with modifications (e.g., adding numbers).
Brute-force attack
Why wrong: Brute-force would try all possible passwords, not just a dictionary list.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Dictionary attack
This is a dictionary attack because the attacker uses a predefined list of common usernames and passwords (a dictionary) against the SSH service. Unlike a brute-force attack that tries all possible combinations, a dictionary attack only tests likely entries from a wordlist, making it faster but limited to the dictionary's contents.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Rainbow table attack
Why it's wrong here
Rainbow tables are used offline against hashes, not online login attempts.
Dictionary attack
Why this is correct
Using a list of common passwords against usernames is a dictionary attack.
Related concept
Read the scenario before looking for a memorised answer.
Hybrid attack
Why it's wrong here
Hybrid attacks combine dictionary words with modifications (e.g., adding numbers).
Brute-force attack
Why it's wrong here
Brute-force would try all possible passwords, not just a dictionary list.
Common exam traps
The trap here is confusing a dictionary attack with a brute-force attack; CEH emphasizes that a dictionary attack uses a wordlist of likely passwords, while a brute-force attack exhaustively tries all possible character combinations, regardless of likelihood.
Detailed technical explanation
SSH authentication typically uses PAM (Pluggable Authentication Modules) to validate credentials; a dictionary attack against SSH often targets the 'sshd' daemon, which logs failed attempts in /var/log/auth.log. Tools like Hydra or Medusa can automate this by sending SSH_MSG_USERAUTH_REQUEST packets with username/password pairs, and the server responds with SSH_MSG_USERAUTH_FAILURE for invalid credentials. In real-world scenarios, attackers may use leaked credential databases (e.g., from previous breaches) as their dictionary, increasing success rates against reused passwords.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Enumeration and System Hacking — This question tests Enumeration and System Hacking — Read the scenario before looking for a memorised answer..
The correct answer is: Dictionary attack — This is a dictionary attack because the attacker uses a predefined list of common usernames and passwords (a dictionary) against the SSH service. Unlike a brute-force attack that tries all possible combinations, a dictionary attack only tests likely entries from a wordlist, making it faster but limited to the dictionary's contents.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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