This CS0-003 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.
A security analyst is reviewing SIEM alerts and sees multiple failed logon events from a single external IP address across several user accounts within two minutes. The source IP is from a known malicious geolocation. 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.
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
The scenario describes multiple failed logon attempts from a single external IP against several user accounts within a short time window. This pattern is characteristic of a brute-force attack, where an attacker systematically tries common or guessed passwords across multiple accounts to gain unauthorized access. The single source IP and rapid sequence of failures distinguish it from a password spraying attack, which spreads attempts across many accounts slowly to avoid lockout thresholds.
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.
✗
Password spraying attack
Why it's wrong here
Password spraying uses a single password against many accounts, but the source IP is usually not the same across attempts.
✗
Distributed denial-of-service (DDoS) attack
Why it's wrong here
DDoS targets network availability, not authentication.
✓
Brute-force attack
Why this is correct
Multiple failed logon attempts from one IP across accounts indicates a brute-force attack.
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.
✗
Pass-the-hash attack
Why it's wrong here
Pass-the-hash uses stolen hashes and does not generate failed logon events.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing a brute-force attack with a password spraying attack; CompTIA often tests this by emphasizing the speed and source IP concentration versus the slow, distributed nature of password spraying.
Detailed technical explanation
How to think about this question
In a brute-force attack, the attacker typically uses automated tools like Hydra or Medusa to iterate through password lists against a target authentication service (e.g., RDP, SSH, or web login). SIEM correlation rules often detect this by counting failed logon events from a single source IP exceeding a threshold within a defined time window (e.g., 10 failures in 60 seconds). Real-world mitigations include account lockout policies, IP-based rate limiting, and multi-factor authentication, which force attackers to slow down or switch to distributed sources.
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 CS0-003 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: Brute-force attack — The scenario describes multiple failed logon attempts from a single external IP against several user accounts within a short time window. This pattern is characteristic of a brute-force attack, where an attacker systematically tries common or guessed passwords across multiple accounts to gain unauthorized access. The single source IP and rapid sequence of failures distinguish it from a password spraying attack, which spreads attempts across many accounts slowly to avoid lockout thresholds.
What should I do if I get this CS0-003 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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.
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Question Discussion
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