The correct answer is a brute-force attack because the authentication logs show multiple failed SSH login attempts originating from various IP addresses while cycling through different usernames, which is the hallmark of an automated credential stuffing or password guessing campaign. Unlike a DDoS attack that would flood the network with traffic rather than target login prompts, or a man-in-the-middle attack that requires intercepting communications, or a phishing attack that relies on tricking users into revealing credentials, this pattern of distributed, repeated authentication failures directly indicates a brute-force attempt to gain unauthorized access. On the CompTIA SecurityX CAS-004 exam, this scenario tests your ability to distinguish between attack types by analyzing log evidence, a common task in the “Threats, Vulnerabilities, and Mitigations” domain. A frequent trap is confusing distributed brute-force attempts with a DDoS, but remember that DDoS targets availability while brute-force targets authentication. Memory tip: “Many IPs, many usernames, many failures equals brute-force.”
CAS-004 Security Operations Practice Question
This CAS-004 practice question tests your understanding of security operations. 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.
Exhibit
Refer to the exhibit.
# grep "Failed password" /var/log/auth.log | tail -5
Feb 27 10:23:01 server1 sshd[1234]: Failed password for root from 192.168.1.10 port 22 ssh2
Feb 27 10:23:05 server1 sshd[1235]: Failed password for root from 192.168.1.10 port 22 ssh2
Feb 27 10:23:10 server1 sshd[1236]: Failed password for admin from 10.10.10.5 port 22 ssh2
Feb 27 10:23:15 server1 sshd[1237]: Failed password for root from 192.168.1.10 port 22 ssh2
Feb 27 10:23:20 server1 sshd[1238]: Failed password for user from 172.16.0.20 port 22 ssh2
Based on the exhibit, what type of attack is most likely occurring?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Refer to the exhibit.
# grep "Failed password" /var/log/auth.log | tail -5
Feb 27 10:23:01 server1 sshd[1234]: Failed password for root from 192.168.1.10 port 22 ssh2
Feb 27 10:23:05 server1 sshd[1235]: Failed password for root from 192.168.1.10 port 22 ssh2
Feb 27 10:23:10 server1 sshd[1236]: Failed password for admin from 10.10.10.5 port 22 ssh2
Feb 27 10:23:15 server1 sshd[1237]: Failed password for root from 192.168.1.10 port 22 ssh2
Feb 27 10:23:20 server1 sshd[1238]: Failed password for user from 172.16.0.20 port 22 ssh2
A
Man-in-the-middle (MITM) attack
Why wrong: MITM would involve interposition, not authentication failures.
B
Phishing attack
Why wrong: Phishing is social engineering via email, not direct SSH attempts.
C
Distributed denial-of-service (DDoS) attack
Why wrong: DDoS would show high volume of traffic, not repeated login attempts.
D
Brute-force attack
The log shows repeated failed authentication attempts, typical of brute force.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Brute-force attack
Option B is correct because multiple failed SSH login attempts from various IPs with different usernames indicate a brute-force attack. Option A is wrong because DDoS would flood traffic, not authentication attempts. Option C is wrong because MITM would involve interception. Option D is wrong because phishing is social engineering.
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.
✗
Man-in-the-middle (MITM) attack
Why it's wrong here
MITM would involve interposition, not authentication failures.
✗
Phishing attack
Why it's wrong here
Phishing is social engineering via email, not direct SSH attempts.
✗
Distributed denial-of-service (DDoS) attack
Why it's wrong here
DDoS would show high volume of traffic, not repeated login attempts.
✓
Brute-force attack
Why this is correct
The log shows repeated failed authentication attempts, typical of brute force.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
DDoS would show high volume of traffic, not repeated login attempts.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 practitioner preparing for the CAS-004 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
Got this wrong? Here's your next step.
Identify which CAS-004 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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: Brute-force attack — Option B is correct because multiple failed SSH login attempts from various IPs with different usernames indicate a brute-force attack. Option A is wrong because DDoS would flood traffic, not authentication attempts. Option C is wrong because MITM would involve interception. Option D is wrong because phishing is social engineering.
What should I do if I get this CAS-004 question wrong?
Identify which CAS-004 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Based on the exhibit, which type of attack is most likely occurring?
hard
A.Pass-the-hash attack
B.Account lockout attack
C.Replay attack
✓ D.Brute force password guessing
Why D: The exhibit shows a high number of failed authentication attempts (e.g., Event ID 4625) from a single source IP against multiple user accounts over a short period. This pattern is characteristic of a brute force password guessing attack, where an attacker systematically tries common passwords against many accounts to gain unauthorized access. The absence of successful logins or account lockouts further supports this conclusion.
Last reviewed: Jun 24, 2026
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This CAS-004 practice question is part of Courseiva's free CompTIA 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 CAS-004 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.