Quick Answer
The correct answer is credential stuffing, as this attack specifically leverages lists of known username and password pairs obtained from previous data breaches to automate login attempts against a web application. Unlike brute force attacks that guess passwords, credential stuffing exploits the widespread habit of password reuse across multiple services, succeeding because users often employ the same credentials on different platforms. On the Certified Ethical Hacker CEH exam, this concept tests your understanding of post-breach attack vectors and the importance of rate limiting or account lockout mechanisms—the scenario’s lack of these controls is the key vulnerability. A common trap is confusing credential stuffing with brute force attacks; remember that credential stuffing uses valid, previously compromised credentials, while brute force tries to guess them. For a quick memory tip, think “stuffed from a previous breach” to distinguish it from other login-based attacks.
This CEH practice question tests your understanding of web application and injection attacks. 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.
An attacker discovers that a web application's login form allows unlimited login attempts. The attacker uses a list of usernames and passwords obtained from a previous breach to gain access. This attack is known as:
Password spraying
Why wrong: Password spraying uses one password against many accounts.
Brute force attack
Why wrong: Brute force tries all combinations, not using known credentials.
Dictionary attack
Why wrong: Dictionary attack uses a wordlist, not necessarily breached pairs.
Credential stuffing
Using breached credentials to gain access.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Credential stuffing
Credential stuffing (option D) is correct because the attacker uses a list of known username/password pairs from a previous breach to automate login attempts against the web application. This attack exploits password reuse across services, not the weakness of the passwords themselves, and relies on the application's lack of rate limiting or account lockout mechanisms.
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.
Password spraying
Why it's wrong here
Password spraying uses one password against many accounts.
Brute force attack
Why it's wrong here
Brute force tries all combinations, not using known credentials.
Dictionary attack
Why it's wrong here
Dictionary attack uses a wordlist, not necessarily breached pairs.
Credential stuffing
Why this is correct
Using breached credentials to gain access.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates confuse credential stuffing with a dictionary attack, but credential stuffing specifically uses known username-password pairs from a prior breach, not a generic wordlist of passwords.
Detailed technical explanation
Credential stuffing typically uses automated tools like SentryMBA or OpenBullet to submit HTTP POST requests with the stolen credentials to the application's login endpoint. The attack's success depends on the prevalence of password reuse; even with MFA, if the application does not implement device fingerprinting or anomaly detection, the attacker can gain access before the legitimate user is notified. In real-world scenarios, credential stuffing often targets APIs with JSON payloads, where rate limiting is absent or easily bypassed via IP rotation.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the CEH exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Web Application and Injection Attacks — This question tests Web Application and Injection Attacks — Read the scenario before looking for a memorised answer..
The correct answer is: Credential stuffing — Credential stuffing (option D) is correct because the attacker uses a list of known username/password pairs from a previous breach to automate login attempts against the web application. This attack exploits password reuse across services, not the weakness of the passwords themselves, and relies on the application's lack of rate limiting or account lockout mechanisms.
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
This CEH practice question is part of Courseiva's free EC-Council certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CEH exam.
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