Quick Answer
The answer is to disable password authentication and enforce SSH key-based authentication. This eliminates the entire attack surface for SSH brute force mitigation in the cloud because key-based authentication relies on asymmetric cryptography—such as RSA or Ed25519—which cannot be guessed or cracked through repeated login attempts, unlike passwords. Blocking individual IPs or using tools like fail2ban only addresses the symptom of credential stuffing from multiple sources, not the root vulnerability. On the Certified Ethical Hacker CEH exam, this question tests your understanding of defense-in-depth and the difference between reactive controls (IP blocking) and proactive hardening (eliminating the password vector). A common trap is choosing fail2ban or rate-limiting, but the exam emphasizes that cloud environments with elastic IP pools require a permanent reduction of the attack surface. Memory tip: “Keys, not keepsakes”—once passwords are disabled, there’s nothing left to brute force.
This CEH practice question tests your understanding of wireless, iot and cloud security. 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.
A security analyst detects multiple failed authentication attempts on a cloud-based SSH server from a single IP address. The analyst implements a rule to block that IP. However, the attacks continue from different IPs. Which additional control should be implemented to reduce the attack surface?
Disable password authentication and use SSH key-based authentication.
Keys are resistant to brute-force.
Install fail2ban to automatically block IPs after failures.
Why wrong: Similar to manual blocking, but still vulnerable to distributed attacks.
Implement rate-limiting on SSH connections per IP.
Why wrong: Attackers can use many IPs.
Change the SSH port to a non-standard port.
Why wrong: Not a strong security measure.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Disable password authentication and use SSH key-based authentication.
Disabling password authentication and enforcing SSH key-based authentication eliminates the attack vector of brute-forcing passwords entirely. Since the attacker is using multiple IPs to perform credential stuffing, blocking individual IPs (as done initially) or using tools like fail2ban only treats the symptom, not the root cause. Key-based authentication uses asymmetric cryptography (RSA/ECDSA/Ed25519) and is not susceptible to online guessing attacks, thus permanently reducing the attack surface.
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.
Disable password authentication and use SSH key-based authentication.
Why this is correct
Keys are resistant to brute-force.
Related concept
Read the scenario before looking for a memorised answer.
Install fail2ban to automatically block IPs after failures.
Why it's wrong here
Similar to manual blocking, but still vulnerable to distributed attacks.
Implement rate-limiting on SSH connections per IP.
Why it's wrong here
Attackers can use many IPs.
Change the SSH port to a non-standard port.
Why it's wrong here
Not a strong security measure.
Common exam traps
The trap here is that candidates focus on reactive IP-blocking solutions (fail2ban, rate-limiting) or obscurity (port changing) instead of recognizing that the fundamental vulnerability is the use of passwords, which must be eliminated at the protocol level.
Trap categories for this question
Similar concept trap
Similar to manual blocking, but still vulnerable to distributed attacks.
Detailed technical explanation
SSH key-based authentication relies on a public-private key pair where the server stores the public key and the client proves possession of the private key via a cryptographic challenge (e.g., RSA signature verification). This eliminates the need for a shared secret transmitted over the network, making it immune to password spraying and brute-force attacks. In practice, even with fail2ban or rate-limiting, a determined attacker using a botnet of thousands of IPs can still succeed if password authentication remains enabled.
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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Wireless, IoT and Cloud Security — This question tests Wireless, IoT and Cloud Security — Read the scenario before looking for a memorised answer..
The correct answer is: Disable password authentication and use SSH key-based authentication. — Disabling password authentication and enforcing SSH key-based authentication eliminates the attack vector of brute-forcing passwords entirely. Since the attacker is using multiple IPs to perform credential stuffing, blocking individual IPs (as done initially) or using tools like fail2ban only treats the symptom, not the root cause. Key-based authentication uses asymmetric cryptography (RSA/ECDSA/Ed25519) and is not susceptible to online guessing attacks, thus permanently reducing the attack surface.
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 11, 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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