This CC practice question tests your understanding of security operations. 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.
Exhibit
Mar 15 10:30:22 server sshd[1234]: Failed password for root from 192.168.1.100 port 22 ssh2
Mar 15 10:30:27 server sshd[1235]: Failed password for root from 192.168.1.100 port 22 ssh2
Mar 15 10:30:32 server sshd[1236]: Failed password for root from 192.168.1.100 port 22 ssh2
Mar 15 10:30:37 server sshd[1237]: Failed password for root from 192.168.1.100 port 22 ssh2
Refer to the exhibit. A security analyst sees these logs from a Linux server. Which security control should the analyst recommend to address this pattern?
Mar 15 10:30:22 server sshd[1234]: Failed password for root from 192.168.1.100 port 22 ssh2
Mar 15 10:30:27 server sshd[1235]: Failed password for root from 192.168.1.100 port 22 ssh2
Mar 15 10:30:32 server sshd[1236]: Failed password for root from 192.168.1.100 port 22 ssh2
Mar 15 10:30:37 server sshd[1237]: Failed password for root from 192.168.1.100 port 22 ssh2
A
Enable account lockout after 5 failed attempts.
Why wrong: Lockout can mitigate but attackers sometimes slow down to avoid triggering it; not as strong as 2FA.
B
Disable root login via SSH.
Why wrong: Reduces risk but attacker can target other accounts; does not prevent password guessing.
C
Block the IP address 192.168.1.100 via firewall.
Why wrong: Blocks this attacker but others may attack from different IPs; not a comprehensive solution.
D
Implement two-factor authentication for SSH access.
2FA prevents unauthorized access even if passwords are compromised.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implement two-factor authentication for SSH access.
The logs show repeated failed SSH login attempts from a single IP (192.168.1.100) targeting the root account, which is a classic brute-force attack pattern. Two-factor authentication (2FA) for SSH access is the most effective control because it adds a second authentication factor (e.g., TOTP or hardware token) that an attacker cannot bypass even if they guess the password, thus neutralizing the brute-force attack regardless of the number of attempts or the account targeted.
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.
✗
Enable account lockout after 5 failed attempts.
Why it's wrong here
Lockout can mitigate but attackers sometimes slow down to avoid triggering it; not as strong as 2FA.
✗
Disable root login via SSH.
Why it's wrong here
Reduces risk but attacker can target other accounts; does not prevent password guessing.
✗
Block the IP address 192.168.1.100 via firewall.
Why it's wrong here
Blocks this attacker but others may attack from different IPs; not a comprehensive solution.
✓
Implement two-factor authentication for SSH access.
Why this is correct
2FA prevents unauthorized access even if passwords are compromised.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the distinction between reactive controls (like blocking an IP or locking an account) and proactive controls (like 2FA) that address the root cause of authentication attacks, leading candidates to pick a quick fix like IP blocking instead of the more robust security measure.
Detailed technical explanation
How to think about this question
Two-factor authentication for SSH typically uses PAM modules (e.g., pam_google_authenticator) to require a time-based one-time password (TOTP) in addition to the SSH key or password. Even if an attacker obtains the password through brute-force, they cannot authenticate without the second factor, which changes every 30 seconds. In real-world scenarios, 2FA is often combined with rate-limiting (e.g., fail2ban) to provide defense-in-depth, but 2FA alone stops automated brute-force attacks because the attacker lacks the ephemeral token.
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 security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CC question in full detail.
Security Operations — This question tests Security Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Implement two-factor authentication for SSH access. — The logs show repeated failed SSH login attempts from a single IP (192.168.1.100) targeting the root account, which is a classic brute-force attack pattern. Two-factor authentication (2FA) for SSH access is the most effective control because it adds a second authentication factor (e.g., TOTP or hardware token) that an attacker cannot bypass even if they guess the password, thus neutralizing the brute-force attack regardless of the number of attempts or the account targeted.
What should I do if I get this CC 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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