- A
Requiring longer, more complex passwords to make credentials harder to guess
Why wrong: Credential stuffing uses real, previously stolen credentials — not guesses. Password complexity requirements don't help because the attacker already has working username/password pairs from previous breaches.
- B
Multi-Factor Authentication (MFA/2SV), which requires a second verification factor beyond the password that attackers don't have even when they possess the stolen credentials
MFA is the definitive defense against credential stuffing. The stolen credentials work for the first factor (password), but the attack fails at the second factor (authenticator app TOTP, push notification, hardware security key). Attackers would need both the credentials AND access to the user's second factor device — a much higher bar.
- C
Encrypting passwords in the company's database using bcrypt to prevent the stolen passwords from being usable
Why wrong: Encrypting/hashing passwords in the company's own database protects against an attacker stealing the company's database. Credential stuffing uses credentials stolen from other breached sites where users reused passwords. The company's own password storage is not the attack vector.
- D
Implementing HTTPS on the login page to prevent credentials from being intercepted in transit
Why wrong: HTTPS protects credentials during transmission. Credential stuffing doesn't intercept credentials in transit — it uses previously stolen credentials from other breaches. HTTPS doesn't prevent replay of already-stolen credentials.
Mitigate Credential Stuffing Attacks with MFA
This GCDL practice question tests your understanding of trust and security with google cloud. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 enterprise's security team is implementing a strategy to protect against 'credential stuffing' attacks — where attackers use lists of username/password combinations from previous data breaches to try to log in to the company's applications. Which authentication control most effectively mitigates this threat?
Quick Answer
The answer is Multi-Factor Authentication (MFA/2SV), which most effectively mitigates credential stuffing attacks because it requires a second verification factor—such as a one-time code from an authenticator app, a hardware security key, or a biometric—that attackers do not possess even when they have valid username and password pairs stolen from previous data breaches. This additional layer renders the stolen credentials useless, as the attacker cannot complete the second factor challenge to gain access. On the Google Cloud Digital Leader exam, this concept tests your understanding of how authentication controls defend against automated login attempts; a common trap is assuming that stronger passwords or account lockout policies alone are sufficient, but MFA is the definitive control because it breaks the attacker’s reliance on the password itself. A useful memory tip: think of MFA as the “second lock” that makes credential stuffing fail—without the second factor, the stolen key (password) is worthless.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Multi-Factor Authentication (MFA/2SV), which requires a second verification factor beyond the password that attackers don't have even when they possess the stolen credentials
Multi-Factor Authentication (MFA/2SV) is the most effective control against credential stuffing because it requires an additional verification factor (e.g., a one-time code from an authenticator app, a hardware token, or a biometric) that the attacker does not possess, even if they have valid username/password pairs from a breach. This renders the stolen credentials useless for authentication, as the attacker cannot complete the second factor challenge. In Google Cloud, this is commonly enforced via Identity Platform or Cloud Identity with security keys or TOTP.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Requiring longer, more complex passwords to make credentials harder to guess
Why it's wrong here
Credential stuffing uses real, previously stolen credentials — not guesses. Password complexity requirements don't help because the attacker already has working username/password pairs from previous breaches.
- ✓
Multi-Factor Authentication (MFA/2SV), which requires a second verification factor beyond the password that attackers don't have even when they possess the stolen credentials
Why this is correct
MFA is the definitive defense against credential stuffing. The stolen credentials work for the first factor (password), but the attack fails at the second factor (authenticator app TOTP, push notification, hardware security key). Attackers would need both the credentials AND access to the user's second factor device — a much higher bar.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Encrypting passwords in the company's database using bcrypt to prevent the stolen passwords from being usable
Why it's wrong here
Encrypting/hashing passwords in the company's own database protects against an attacker stealing the company's database. Credential stuffing uses credentials stolen from other breached sites where users reused passwords. The company's own password storage is not the attack vector.
- ✗
Implementing HTTPS on the login page to prevent credentials from being intercepted in transit
Why it's wrong here
HTTPS protects credentials during transmission. Credential stuffing doesn't intercept credentials in transit — it uses previously stolen credentials from other breaches. HTTPS doesn't prevent replay of already-stolen credentials.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The GCDL exam often tests the misconception that password hashing (like bcrypt) or encryption protects against credential stuffing, but candidates must recognize that the attacker already has the plaintext passwords from a prior breach, so hashing the database is irrelevant to this attack vector.
Detailed technical explanation
How to think about this question
Credential stuffing relies on the reuse of credentials across services; MFA breaks this by introducing a time-bound or possession-based second factor that is not shared across breaches. In practice, Google Cloud's Identity-Aware Proxy (IAP) can enforce MFA at the application layer, and services like reCAPTCHA Enterprise can be layered to detect automated login attempts. A subtle behavior is that even with MFA, attackers may attempt to bypass it via session hijacking or phishing, but MFA remains the primary defense against bulk automated login attempts.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Trust and security with Google Cloud — study guide chapter
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FAQ
Questions learners often ask
What does this GCDL question test?
Trust and security with Google Cloud — This question tests Trust and security with Google Cloud — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Multi-Factor Authentication (MFA/2SV), which requires a second verification factor beyond the password that attackers don't have even when they possess the stolen credentials — Multi-Factor Authentication (MFA/2SV) is the most effective control against credential stuffing because it requires an additional verification factor (e.g., a one-time code from an authenticator app, a hardware token, or a biometric) that the attacker does not possess, even if they have valid username/password pairs from a breach. This renders the stolen credentials useless for authentication, as the attacker cannot complete the second factor challenge. In Google Cloud, this is commonly enforced via Identity Platform or Cloud Identity with security keys or TOTP.
What should I do if I get this GCDL question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This GCDL practice question is part of Courseiva's free Google Cloud 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 GCDL exam.
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